Introduction to Community Medicine 1 P ART -I BASIC CONCEPTS IN COMMUNITY MEDICINE 1 . Introduction to Community Medicine 2 . Concept of Health Positive health W ell-being Spectrum of health Determinants of health Indicators of health 3. Concept of Disease Theories of disease causation Epidemiological triad Natural history of disease Iceberg phenomenon of disease 4 .

6 Community Medicine Concept of Health 2 INTRODUCTION Health is defined (by WHO) as A state of complete physical, mental and social well-being of an individual and not merely an absence of disease or infirmity . (infirmity = weakness, feebleness, opposite of firmness). Health is not an end in itself but the means to another end namely to lead socially and economically a productive life. As per the definition, health is three dimensionalthe physical, the mental and the social. Non medical dimensions which can be included are spiritual, emotional, vocational and political dimensions. Physical Dimension A person is said to be physically healthy , when all the or gans and systems in the body are functioning perfectly at their optimum capacity . The signs of physical health are good complexion, a clean skin, bright eyes, lustrous hair , well built, with firm flesh, a sweet breath, a good appetite, sound sleep, regular activity of bowel and bladder and co-ordinated bodily movements. All the systems function normally , all the special senses are intact, the resting temperature, pulse rate, respiratory rate and blood-pressure are all in the normal range for the individual s age and sex. The physical health of an individual can be assessed by the history of having taken treatment or hospitalization for any illness, thorough clinical examination, anthropometric measurements, biochemical and laboratory investigations. Ment al Dimension A person is said to be mentally healthy , when he/she is having a perfect state of balance with the surrounding world, having harmonious relation with others, the intelligence, memory , learning capacity , judgement are normal, not having any internal conflicts, accepts criticism sportively , has got good self-control emotionally , solves the problems intelligently , has full self-confidence, is well adjusted with others and is satisfied with what he possesses. He is cheerful and calm. The mental health of an individual can be assessed by his behavior , and attitude. Social Dimension An individual is said to be socially healthy , when he is accepted, respected and loved by all in the family , by his friends, relatives, neighbourers, colleagues and others. S piritual Dimension This is a holistic dimension. A person is said to be spiritually healthy , when he possesses Sound mind in a Sound body, with the knowledge of philosophy , leading a simple life with a very high level of thinking. Thus spiritual is something which transcends physiology and psychology . Emotional Dimension This is rather difficult to differentiate from mental health. However , a person is said to be emotionally healthy , when he does not loose temper or does not develop tension and has self-control. V ocational Dimension An individual is said to be healthy vocationally , when he is capable of earning suf ficiently to lead the life successfully; POSITIVE HEAL TH A person who is healthy physically , mentally and socially (and spiritually) is said to be in a state of Positive Health, i.e. Highest standard of health.

12 Community Medicine Concept of Disease 3 INTRODUCTION (Dis = opposite, Ease = comfort; health) W ebster defines disease as a condition, in which body health is impaired and performance of vital functions in the body is interrupted. In other-words disease is a physiological or psychological dysfunction of the body . Illness is a subjective feeling of not being well. Sickness is a state of social dysfunction (i.e. inability to perform his social role.) WHO has defined health but not disease, because of the following limitations. Disease has got a spectrum varying from sub-clinical state to severe illness. Onset may be sudden (as in food poisoning) or insidious (as in leprosy). The diseased person may be apparently healthy but may be spreading to others (as in carrier state). The same pathogen may cause more than one disease (e.g. Streptococci). The same disease may be caused by more than one organism (e.g. diarrhoea). The course of the disease may be short or prolonged. It is difficult to demarcate between normal and abnormal state as in hypertension, diabetes, mental illness, etc. The final outcome of the disease is variable, i.e. recovery , disability or death. THEORIES OF DISEASE CAUSA TION Old Theories T ill the end of 18th century , various theories were in vogue, e.g. Supernatural theory of disease (e.g. curse of God; an evil eye). The A yurveda considers that the disease is due to imbalance of the tridoshas. These are V ata (air), Pitta (bile) and Kapha (mucus). The Chinese medicine believes that the disease is caused due to imbalance of male principle (Y ang) and female principle (Y in). Germ Theory of Disease The discoveries in microbiology at the turn of 18th century became a turning point in the etiological concept of disease. Louis Pasteur (1860) demonstrated the presence of bacteria in the air . Robert Koch (1877) showed that anthrax was caused by bacteria. These discoveries of Pasteur and Koch confirmed the germ theory of disease. Many microbes were discovered in quick successiongonococcus in 1847, typhoid bacillus, pneumococcus in 1880, tubercle bacillus in 1882, cholera-vibrio, in 1883, diphtheria bacillus in 1884 and so on. Koch s postulates must be fulfilled before any micro- organism is considered as necessary cause for any disease. The postulates are: The organism must be constantly associated with the lesions of the disease. It should be possible to isolate the organism from the lesions. Inoculation of the isolated organism into the experi- mental animal should reproduce the lesions of the disease. It should be possible to re-isolate the organisms in pure culture from the lesions produced in experimental animals. Thus the emphasis has shifted from empirical causes (like bad air as cause in malaria) of old theories to microbes of Germ theory . But now it is recognized that a disease is rarely caused by a single agent alone, but depends upon a number of contributory factors.

Concept of Prevention 4 INTRODUCTI ON The objective of community-medicine is to oppose the disease process in order to preserve the health, promote the health, prolong the life and to minimize the suf ferings by preventing the occurrence of the disease. The disease can be prevented by opposing its natural history at dif ferent levels. There are three levels of prevention-Primary , Secondary and T ertiary . PRIMAR Y PREVENTION This is the measure undertaken in the period of pre- pathogenesis (i.e. before the development of the disease) which removes the possibility of occurrence of the disease. Specially it is all the more important in those diseases, for which no treatment is available, e.g. AIDS, cancer , rabies, carries tooth, etc. Primary prevention can be adopted by two modes of interventionnamely Health promotion and Specific protection. Health Promotion This consists of general measures, which will strengthen the individual/host and prevents the occurrence of the disease by interrupting the interaction among the three factors of epidemiological tried . The various measures of health promotion are: Health education (on personal hygiene, oral hygiene, nutrition education, life-style etc), Sex education, Adequate nutrition, Improvement in the environmental sanitation (such as control of insects, provision of protected water supply , sanitary disposal of sewage etc), Promotion of breast-feeding and proper weaning, Family planning and spacing of births, Genetic counseling (premarital and marriage coun- seling), E f ficient ante-natal care and post natal care, Recreation facilities (sports, games, cultural activities etc), Improvement in the literacy level, Y oga exercises and meditation. Specific Protection This consists of specific measures, which prevent specific diseases. The various measures are: Immunization against vaccine preventable diseases, Silver nitrate or Penicillin eye drops against ophthalmia neonatorum, C ondom against AIDS, Use of specific nutrients (V it. A against nutritional blindness, IF A against nutritional anemia, Iodised salt against Iodine Deficiency Disorders), Helmet against head-injury , Masks against pneumoconiosis, Ear plugs against noise induced deafness, Lead apron against radiation hazards, V isor against welding keratitis, Barrier cream against occupational skin cancer , A voidance of aller gens and carcinogens, S terilization procedures of sur gical instruments, Pasteurization of milk, T raf fic signals against road accidents, Quality control of foods, drugs and cosmetics, etc. These measures need to be applied in specific situation for specific groups. They are more concrete and effective.

Water 21 P ART -II 5 . W ater Impurities W ater cycle W ell Health hazards of water contamination Purification of water Hardness of water Conservation of water resources Sanitary analysis of water 6 . Air and V entilation Effects of vitiated air Indicators of thermal comfort Air pollution V entilation 7 . Noise Hazards of noise pollution Prevention and control of noise pollution 8 . Light Measurement of light Health hazards of lighting 9 . Radiation Nonionising radiations Ionising radiations Prevention and control of radiation hazards 1 0 . Housing Housing standards Housing and health Indicators of housing Measures to solve the housing problem 1 1 . M eteorology Atmospheric pressure Air temperature Humidity Air movement 12. Disposal of W astes Methods of refuse disposal Disposal of excreta W ater carriage system Disposal of sullage Disposal of sewage 13. Management of Hospital W aste The objectives of the waste management system Legislative framework S trategies adopted for hospital waste management A vailable tr eatment and disposal technologies Existing avialable technologies DOs and DONT s of health car e waste 1 4 . Medical Entomology Classification of arthropods Arthropod borne diseases Principles of arthropod control Mosquitoes Flies Fleas Lice Bugs Ticks Mites (Chiggers) Cyclops Disinsection Insecticide tox icity 1 5 .

Air and V entilation 6 INTRODUCTION Air constitutes the immediate physical environment. It is such an important environment that without air , life would not have existed on earth. The public health importance of air is that not only it is necessary for breathing purposes, cooling of the body , hearing and smelling but also it acts as a vehicle of transmission of diseases, resulting in even epidemics and pandemics. Air is a mixture of gasses, mainly nitrogen (78%), oxygen (21%) and carbon-dioxide (0.03%), remaining by other gasses such as argon, neon, helium, xenon, etc. Strictly speaking there is no pure air . Air always contains foreign substances in the form of solid liquid (moisture) and gasses, at all times, in all places. Air is said to have become polluted when it contains these foreign substances such as dust, becteriae, spores gasses etc in excessive concentration, so as to affect the health of human beings and animals and causes damage to plants and properties. Changes in the Air Due to Human Occup ancy Due to human occupancy , the air in the room is vitiated. The changes that take place in the air of such an occupied room are physical and chemical. The physical changes are i . Rise in the temperature due to emanation of body heat. i i . Rise in the relative humidity due to expiration and perspiration. iii. Decrease in the air movement. i v . Occurrence of unpleasant odors arising from expi- ration, perspiration, bad oral hygiene, dirty clothes and other sources. v . Bacterial pollution by the infected droplets. The chemical changes are: i . Increase in the CO 2 concentration i i . Decrease in the O 2 concentration. The vitiation of air affects the health, comfort and efficiency of occupants mainly due to physical changes in the air . EFFECTS OF VITIA TED AIR They are divided into acute and chronic. Acute effects are lassitude, head ache, nausea, vertigo, vomiting and even collapse. Death may occur in extreme cases. Chronic ef fects are anemia, debility , digestive distur - bances, nutritional and metabolic disorders, lowered vitality and decreased resistance to infections. The working efficiency is decreased and the output of the work falls. The effects of vitiation of air was first observed by Sir Leonard Hill. INDICA T ORS OF THERMAL COMFORT Air T emperature This alone is not an adequate indicator . Air T emperature and Humidity This is a better indicator than air temperature alone but still this is unsatisfactory . Air T emperature, Humidity and Air Movement These three together is called Cooling Power of the air , which can be measured by a device called Kata thermo- meter.

Noise 7 INTRODUCTION Noise is an unwanted sound, causing disturbance or annoyance to the hearer . Therefore, noise is a nuisance. The term Noise pollution signifies the cacophony of sounds that are being produced in the modern life, leading to health hazards. Noise has two measurable propertiesFrequency and Intensity . Fr equency : It is the number of complete vibration cycles per second. It is measured in the units called Hertz (Hz). One Hz is equal to one wave per second. This determines the pitch of the sound. The normal, human audio-frequency range (audible range) varies from 20-20,000 Hz. Below 20 Hz are infra-audible (infrasounds) and above 20,000 Hz are called ultrasounds (ultrasonic). Intensity : It is the amplitude of the vibrations (i.e., loudness) of the sound and is measured in units of Decibels (dB) (Bel in memory of Alexander Graham Bell). Decibels are recorded in noise meter (Fig. 7.1). Noise Level V alues Whispering 2 0 t o 3 0 d B Normal conversion 30 to 65 dB (Maximum upper limit is 85dB) Street traffic 60 to 80 dB Shouting about 100 dB Motor car horn, boiler factories about 120 dB Train, aeroplane engine about 120 dB Threshold of pain about 140 dB Jet plane about 150 dB Mechanical damage 150-160 dB Fig. 7.1: A public noise metre Instruments used in the Study of Noise Sound level metermeasures the intensity of sound in decibel (dB). Octave band frequency analyzerindicates whether the intensity is high pitched or low pitched. Audiometermeasures the hearing ability . Zero line at the top of the audiogram represents normal hearing. HAZARDS OF NOISE POLLUTION Grouped into two groupsAuditory and Nonauditory . Auditory Effects Quantifiable Threshold shift (temporary , later permanent). Auditory fatigue (associated with whistling and buzzing). Deafness (temporary or permanent) (occupational deafness).

Light 8 INTRODUCTION Light constitutes an important physical environment of human beings. It is also a form and a source of ener gy . W ithout light, living will not be comfortable. It is essential for vision. Light may be from natural source or artificial source. Natural source of light is the Sun. The visible rays of the sunlight constitutes the solar spectrum VIBGYOR, which can be seen in the rainbow . The sun rays beyond the spectrum are invisible the rays beyond the violet end are Ultraviolet rays and the rays beyond the red end are Infra- red rays. Both have got therapeutic uses. For carrying out the work efficiently with efficient vision, following Day light factors are essential. Sufficient illumination of 15-20 foot candles Uniform distribution in the working place Absence of glare (i.e., Glare is excessive contrast e.g. headlight of a vehicle at night. The same light during dry time does not cause glare because of absence of contrast) Absence of sharp-shadows Steadiness of source of light White color of the light Contrast surroundings. MEASUREMENT OF LIGHT The luminous intensity or power of artificial light is measured by the standard Candle. The amount of light given off by the burning of a spermwax candle burning 120 grains per hour is called one candle power . The illumination received from one candle at a distance of 1 foot, is known as 1 ft. candle. The illumination is measured by an instrument called photometer . A minimum of at least 6 ft. candle illumination is required for clear visibility for performance of work. The light is also measured by other parameters such as Luminous flux (flow of light), expressed in lumens Illumination (amount of light reaching a surface) expressed as lux per unit area Luminance (brightness i.e., amount of light reflected from a surface) expressed as lamberts. Natural Lighting This is obtained not only from the sky but also from reflection. Natural lighting depends upon the time of the day , season, weather and atmospheric pollution. Measures to Improve Natural Lighting The buildings should be directed toward North and South, so that there will be uniform lighting from morning to evening. Construction of windows must be properly planned. A tall narrow window gives greater penetration of light and a broad window gives greater diffusion of light. Inside the rooms, the ceiling should be white, the upper portion of walls should be light colored and lower portion should be slightly dark colored. Artificial Lighting Electric light is the best method of providing artificial illumination. There is no combustion, nor there is any reduction in the oxygen content of atmosphere. It gives good, steady and bright light. The different types of electric lights are Filament lamps (Incandescent lamps): In this type, the tungsten filament is heated and light is emitted. Only 5 percent of the current is available for lighting and remaining 95 percent is expended as heat.

Radiation 9 INTRODUCTION Radiation also constitutes an important physical environment. Radiation is defined as a form of ener g y , emitted from a matter , in all directions, in the form of waves, each wave carrying a quantum of energy or emitted in the form of fast moving sub-atomic particles or nucleotides. Such energy is emitted from a matter as a result of electrical excitement or internal changes. The energy that is emitted depends upon the wave-lengths. Shorter the wave-length, grater is its ener gy value and vice-versa. W ave lengths are expressed as  . Radiations are grouped into two groupsnamely Ionising and Nonionising radiations, depending upon the ability to penetrate the tissue, deposit its energy and cause destruction of the tissue or not respectively . NONIONISING RADIA TIONS These do not penetrate the body tissues but they are absorbed by the superficial tissues like skin and eyes. Depending upon their increasing wave length (or decreasing frequency) they are classified as follows: Rays W ave lengths (in millimicr ons or nanometer 1 nm = 1/1000 mm) Ultra-violet rays 20-400 nm V isible light 400-700 nm Infra-red rays 700-1000 nm (-1mm) Micro-waves 1mm 1 metre Radiofrequency waves 1 mtr 1 km Laser radiations Ultraviolet Rays Sources Natural source is Sun. As they are coming from Sun, maximum rays are absorbed by ozone of the atmosphere. But still the effects are more at higher altitudes than at sea level and in summer than in rainy days. Artificial sources are many , such as mercury vapor tubes, carbon-arc, electric welding, etc. High Risk Persons For natural sources, are farmers, shepherds, sailors, road builders, fishermen and those skating on snow . For artificial sources, are electric welders, cinema projector workers. Hazards Since the UV rays do not penetrate the tissues but are absorbed, the effects are primarily on the skin and eyes. From the natural sources, the effects are more on the skin and from the artificial sources, the effects are more on the eyes. The effects depends upon the duration of exposure, intensity of exposure and the individual susceptibility . On the Skin i . Short-term effects and i i . Long-term effects. i. Short term effects : These are immediate effects as follows: Melanin pigment which is normally present in malphigian layer migrates upwards into the corneum causing darkening of the skin (Suntan) Histamine is released resulting in erythema, edema, blisters and even ulcers depending upon the quantity released Thickening of all layers of epidermis, a protective mechanism Synthesis of vitamin D takes place and rickets is prevented (the last two are useful to the body).

Housing 10 INTRODUCTION Housing is defined as a physical structure which provides safety , security and shelter to the members living in and the environment including services and facilities necessary for maintaining optimum health by those members. It is the place where the members spend most of their life-time and are reared, thus determining the culture (social and civil life) of the family . Requir ements of a house: A. Location : The house should be located on dry , non- caving ground, having an independent unit and should be nearer to shopping place, recreational facilities, educa- tional centers, emergency services and transport system. B. Construction : The house should be so strongly con- structed as to withstand the vagaries of nature such as landslide, floods or earth-quake, etc and also it should be safe and secured. C. Sanitation : From the point of view of health, there should not be over-crowding and there must be sufficient light and ventilation, sufficient water supply and proper arrangements for drainage of liquid waste in the house. Provision should be made for insect proofing and rodent proofing also. Cleanliness to be maintained in and around the house. D. Comfortable house-life : For this, there must be ideally separate kitchen, store room, bed rooms, a common living room for the entire family and a corridor . HOUSING ST ANDARDS These vary from country to country , depending upon the socioeconomic status, family size and composition, cultural practices and climate conditions. The standards recommended in India are as follows: Site selection : The site or the ground selected should be high and only to drain the water . The soil should be of gravel nature. Made-soil (i.e. ground leveled by dumping refuse) and damp-sites should be avoided. It should have proper approach roads and away from traffic and industries. Foundation : This must always be solid and substantial. The foundation is laid with a bed of cement concrete over the stones to cover the trench. The object is to prevent subsidence of the building. The width of the foundation should never be les than 25 inches. In addition to this bed of concrete, a layer of imper- vious material known as damp proof course should be laid horizontally , along the entire thickness of each wall at plinth level. This prevents the upward progress of the moisture. W alls : The walls are constructed with cement and bricks or stones, with a minimum thickness of 9 inches, obtained by laying the bricks lengthwise and cross-wise in alternate layers. The walls are then plastered so that it should neither absorb heat nor it should conduct the heat. Painting of the walls renders the surface impervious and enables easy wash. Floor : Floor should be air and water tight, surface should be smooth, facilitate easy wash and should be damp- proof. The concreted floor should be covered with patent stone slabs or in better class houses, with marble slabs or tiles. Roof : Flat roofs should have sufficient slope to drain rain water . Height of the roof should not be less than 10 feet, as the heat radiated from the roof is in inverse ratio to the square of its distance.

Meteorology 11 INTRODUCTION Meteorology is the science that deals with the study of changes or phenomena occurring in the atmosphere. The components of meteorological environment are: Atmospheric pressure, Air temperature, Humidity . Air movement (Air velocity) (Direction and speed of the wind) Rain fall. The net effect of all these elements on the health and well-being of human life, animal life and vegetable life for the period of a month or year is called Climate and with reference to a particular stated period or time, is called W eather . ATMOSPHERIC PRESSURE The atmosphere (envelope of the air) is about 200 miles thick (320 km). The air of the lower level is much denser and heavier than the upper layer . The atmospheric pressure at sea level is 760 mm Hg. This is called One atmosphere of pressure. The atmospheric pressure falls as the altitude increases as in high mountains and rises as altitude increases as in high mountains and rises as altitude decreases as in deep mines. Thus at an altitude of 1,00.000 feet above the sea level, the at pressure is less than 10 mm Hg and for every 33 feet below the sea level, the atmospheric pressure increases at the rate of one atmosphere. i.e. when a person descends 33 feet (as in mines), he is exposed to an atmospheric pressure of 2 atmospheres i.e., 760 × 2 = 1520 mm of Hg. The instrument used to measure atmospheric pressure is called Barometer . Kew Pattern S tation barometer is widely used. Others are Fortin s barometer , Aneroid barometer and Barograph. Aneroid Barometer The name aneroid means devoid of fluid. It does not contain mercury or any other fluid. It consists of a cylindrical metal box with partial vacuum. It has an elastic metal top which is sensitive to changes in the atmospheric pressure (Fig. 1 1.1). The pressure changes are transmitted from the metal top to a pointer through a series of springs. The pointer moves on a dial and indicates atmospheric pressure. It is not a precise instrument. Since it is a handy apparatus, it is used while climbing the mountains or in aeroplane. Barograph It is a modified aneroid barometer , in which the pointer records the pressure changes on a graph continuously . Effects on Health The influence of atmospheric pressure on health is considered under two headings. Fig. 1 1.

Disposal of W astes 12 The waste products of the community living are refuse, human excreta and sewage. Refuse It is a solid waste. It is of the following types: S treet refuseconsists of leaves, straw , papers, animal dung and litter of all kinds. Market refuseconsists of putrid vegetables and animal matters. Domestic refuseconsists of ash, rubbish (pieces of papers, clothes, wood, metal, glass and dust and dirt) and garbage (waste arising from the kitchen, such as peelings of vegetables, waste food, rotten fruits and vegetables etc.). Industrial refuseconsists of wide variety of toxic chemical compounds. Stable litterconsists of mainly animal dung and left over animal feeds from animal stables. Health Hazards Pollution of water , soil, Contamination of food and drinks through dust and flies, Decomposed refuse favours propagation of house files, Attracts rodents and vermin. Nuisance by sight and smell. Storage of Refuse Dustbins made of galvanized iron sheets are suitable receptacles, placed at a fair distance from the house. If it is covered with a lid, people will not open it but throw the refuse around it. If not covered, the dogs, pigs and other animals scatter the contents, thus creating nuisance. In the developed countries, the dustbins will have paper sack. When the paper sack is filled, it is removed from the bin and a new sack is placed inside. The municipal workers remove the refuse periodically . Collection of Refuse House to house collection of refuse is the best method but that is not done. Dumping the refuse in the public dustbin is also not done properly . As a result, refuse is dispersed all along the street. The Environmental Hygiene Committee (1949) recommends House to house collection of refuse, Open refuse carts should be replaced by enclosed vans, Mechanical transportation is more practical and economical. The collection and transportation of refuse should be carried out during the early hours of the morning to minimise the nuisance. Wheel barrows are small hand pushed carts used to collect refuse from narrow lanes where big carts cannot go. The refuse collected by wheel barrows is deposited in dustbins. Collection and removal of domestic and town refuse, apart from human excreta, by means of manual labor is called scavenging. METHODS OF REFUSE DISPOSAL There are many methods. But choice depends upon the cost factor and the availability of land and labor . The dif ferent methods are: a . Dumping b . Controlled tipping.

Any waste generated out of hospitals can be said to be Hospital W aste. Any waste generated consequent to health care activity including those at home is Health care waste. According to Biomedical W aste (Management and Hand- ling) Rules 1998, of India, Biomedical W aste (BMW) is defined as a waste generated during diagnosis, treatment, immunization of human beings or animals or in research activities pertaining thereto or in the production or testing of biologicals. Thus Biomedical W aste encompasses a wider category of waste and includes waste from veterinary institutions and slaughter houses also. However , radioactive waste is not included under BMW . INTRODUCTION Hospitals generate large volumes of wastes as a by-product of a variety of health services and procedures carried out such as sur gery , dressing of the wounds, dialysis, deliveries, laboratory and dental procedures, postmortem procedures, etc. Such a waste may be infectious or non-infectious. If such a waste is not collected, transported and disposed off, it not only results in causation of Hospital Acquired Infections (Nosocomial infections) but also poses a major public health hazard by causing pollution of air , water and soil. Persons who are constantly exposed to these wastes especially waste-sharps, are hospital workers (nurses), rag pickers cleaners, laundry staff, etc who are always at a risk of getting fatal diseases like Hepatitis B and C and HIV through injuries by contaminated needles and sharps as an occupational hazard. Indiscriminate dumping of the hospital wastes into the backyards or into open municipal pits, become breeding places for disease spreading mosquitoes, flies, rodents and microbes. Epidemics can result from the contamination of drinking water and food sources with these infectious wastes, which are washed by rains. Indiscriminate open burning of infectious waste, especially plastics will result in emission of noxious gasses, which may produce cancer . Further , there is scope for (improper) re-use of syringes, needles, polythene bags, catheters and other rubber tubes, bottles, etc. Not all the waste from a heath care setting is infectious or hazardous. There is a mixture of different types of waste. The twin problems of Health Care W aste are its characteris- tics and quantity . Characteristics of Health Care W aste It is estimated that about 10-15 percent of Health Care W aste is Infected W aste. Noncontaminated or non-infectious waste becomes infected when it gets mixed with infected waste. Hence one should not allow mixing of infected waste with household (non-contaminated) waste. This is possible only if the waste is segregated or sorted into Infected and Household waste at the source or point of generation. Quantity of Health Care W aste This depends upon the type of health care setting and the services offered. A survey of wastes generated in different health care settings (waste survey) is a basic pre-requisite for planning and implementing a waste management endeavour . This is known as W aste Audit. W ith an estimated 0.5 to 1.0 kg of wastes per bed per day , state hospital like Community Health Centers, T aluka Hospitals and Sub-District Hospitals with bed strength of 30-100 can produce 15-50 kg of wastes per day , whereas District and T eaching Hospitals including private hospitals in urban cities may need to handle 200-1000 kg of hospital wastes daily .

Medical Entomology 14 It is that branch of community medicine, which deals with the study of arthropods of medical importance. The term arthropoda is derived from two Greek words : arthron means jointed and poda meaning foot. Accordingly arthropods are creatures having jointed legs. Their other features are absence of vertebrae, bilateral symmetrical body consisting of segments, chitinous exoskeleton and power of ecdysis. (i.e., moulting). Internally the body is filled with colorless fluid called Hemocele, in which the internal organs are bathed, the heart dorsally , the central nervous system ventrally and the alimentary canal in between. Respiratory system consists of air tubes, which open by a series of pores called spiracles. Sexes are separate. The medical importance is that they transmit the diseases directly or indirectly . Directly they can act as parasites and indirectly they can spread the diseases from other persons or animals, by acting as vectors or carriers of disease. Their bites and stings may result in urticaria, scratch injuries and even secondary infection. CLASSIFICA TION OF ARTHROPODS The phyllum arthropoda consists of three important classes Class Insecta, Arachnida and Crustacea. Their distinctive features are as follows. V ector: It is an arthropod capable of transmitting or spreading the disease. There are two types of vectors, depending upon the mode of transmission of disease namely mechanical vector and biological vector . A. Mechanical vector: It is an arthropod, which passively transmits the pathogens without biting. For example: House fly mechanically lifts up the pathogens from the filthy substances and deposits over the eatables and contaminates the food. B. Biological vector: It is an arthropod, which transmits the pathogens indirectly by biting the reservoir and sucking the blood containing pathogens. Subsequently the pathogens undergo biological development inside the body of the vector for a specified period, only after which the vector can spread the disease. For example: Mosquito, rat flea, cyclops, etc. The biological transmission are of three types: i. Propagative: In this type, the pathogens undergo multiplication inside the body of the vector . E.g.: Plague bacilli in rat flea, yellow fever virus in rat flea, yellow fever virus in aedes mosquito. ii. Cyclopropagative: In this type, the pathogens undergo not only multiplication but also cyclic development Insecta Arachnida Crustacea 1. Body shape Cylindrical Circular or oval Pear shaped 2. Body division Head, thorax and abdomen Cephalothorax and abdomen Cephalothorax and abdomen 3. Antennae in head 1 pair Absent 2 pairs 4 . Wings Some are winged, some are wingless. Absent Absent 5 . Legs 3 pairs 4 pairs 5 pairs 6 . Living O n land On land In water 7 . Examples Winged Mosquitoes C yclops Flies Ticks Crabs* Wingless Fleas S p i d e r s * Lobsters* Lice Scorpions* Prawns* Bugs * These do not transmit any disease.

Nutrition and Health 15 INTRODUCTION Food: It is a substance consumed, other than water and drugs, for maintaining the health, well-being and vitality of the individual. Sometimes foods are eaten raw . But most of the time, they are eaten after some culinary processes such as cooking, boiling, frying, baking etc. After such treatment, the food becomes diet (meal). Nutrient: It is a chemical factor (active ingredient) present in food item, which determines the quality of food and in turn the health of the individual. For example, Proteins, fats, carbohydrates, vitamins and minerals. Nutrition: It is that branch of science, which deals with the study of a dynamic process, in which the consumed food is utilized for nourishing the body (a process of assimilation of food). Dietetics: It is the science that deals with the study of nutrition in health and disease (i.e. Planning of meals for the healthy and the sick). Balanced diet: It is the diet consisting of right kinds of foods in right proportions, as to provide the required energy and proximate principles for maintaining the health, vitality and well-being and makes smaller provision to withstand short duration of illness. All the nutrients together with water form the main bulk of food. The human body is built up from all the six constituents (5 types of nutrients and water). Man is a mass of pr oteins (muscles), built upon minerals (bones), pr otected by fats (adipose tissue), ener gized by carbohydrates and activated by vitamins CLASSIFICATION OF FOODS By origin: Foods of animal origin; Foods of vegetable origin. By chemical composition: Proteins, fats, carbohydrates, vitamins and minerals. By function: Body building foods (Foods rich in proteins. For example, Meat, fish, milk, egg, pulses, etc.). Energy yielding foods (Foods rich in fats and carbohydrates. For example, Cereals, sugar , ghee, oil, etc.). Protective foods (Foods rich in vitamins and minerals. For example, Fruits, vegetables, etc.). By nutritive value: Cereals and millets, pulses, vegetables, nuts and oil seeds, fruits, animal foods, fats and oils, sugar and jaggery , condiments and spices, miscellaneous foods. NUTRIENTS These are grouped into two groupsMacro- and Micronutrients. Macronutrients: They are so called because they are required in large quantities and so they constitute the main bulk of the food. They are often called as Proximate principles. For example, Proteins, fats and carbohydrates. Their contribution in the food is as follows. Proteins 7 to 15 percent Fats 10 to 30 percent Carbohydrates 65 to 80 percent Micronutrients: They are so called because they are required in small quantities (varying from micro-grams to milli-grams). For example, V itamins and minerals.

Occup ational Health 16 INTRODUCTION W orking population constitutes the major portion of the community . They determine the progress and development of the country . In other words, their health status is considered as a sensitive indicator for the development of the country . Just like home, the place of work is also an important environment for an earning person. Such a person spends nearly 6 to 8 hours a day in the working place till the retirement for about 3 decades. Not only the worker should be healthy but also the working environment should be healthy , safe and free from harmful agents. It is becoming more complicated as man is becoming more ingenious because of industrialization and urbanization. So a worker in all occupations needs special health care delivery . Industrial health is different from occupational health. Industrial health deals with workers in industries and mines, whereas occupational health is concerned with man in any occupation. So it is with reference to all types of employment such as industries, mines, agriculture, forestry , service trades, offices, schools, colleges, mercantile and commercial enterprises etc. Thus industrial health is a component of occupational health. According to Joint ILO/WHO Committee occupational medicine is defined as that branch of community medicine, which deals with the study of health promotion, health protection and maintenance of highest degree of physical, mental and social well-being of workers in all occupations. Thus, occupational health/medicine is application of preventive medicine in all places of employment. But industrial workers are given special attention by the Government, because they work in hazardous environment and are exposed to special risks. If the working environment is healthy , it is not only beneficial for the worker (employee) but also for the employer . There will be mutual benefit for both because there will be increased ef ficiency , increased production and decreased accidents. The subject envisages health, safety and welfare of all workers. Bernardino Ramazzini (1633-1714) of Italy was the first person to stress the importance of taking occupational history of a patient. He wrote on occupational diseases. He is considered as Father of Occupational Health. Aims T o increase the ef ficiency T o increase the production T o decrease the accidents. Objectives T o promote the health of the workers T o maintain the highest degree of physical, mental and social well-being of the workers T o prevent the diseases by elimination of factors which are inimical to their health. ERGONOMICS It is a new concept in occupational health. It is concerned with human engineering. It is derived from Greek words, Er gon means work and Nomos means law . It simply means fitting the job to the worker . That means placing the worker in an environment (job), which is adopted to his physiological and psychological capacity . The main object of ergonomics is to achieve the best mutual adjustment between the man and the machine, which are complimentary to each other , so that there is increased ef ficiency , increased production and decreased accidents in the industry . This term was coined in a conference at Stockholm in 1961, conducted by International Er gonomics Association.

Principles and Practice of Epidemiology 233 P ART -III EPIDEMIOLOGY 1 7 . Principles and Practice of Epidemiology Definition Objectives of epidemiology Epidemiological approach Scope of epidemiology Measurement of morbidity Prevalence rate Measurement of mortality Epidemiological studies Experimental epidemiology Association and causation Uses of epidemiology 18. Infectious Disease Epidemiology Commonly used terms The surveillance system Dynamics of disease transmission Incubation period Investigation of an epidemic Prevention and control of an epidemic Immunizing agents Immunization programme Cold chain Estimation of requirements for immunization Estimation of vaccine efficacy Screening for disease Disinfection T ypes of disinfection Classification of disinfectants S tandardization of disinfectant Disinfection procedures Hospital acquired infections Emporiatrics 1 9 . Epidemiology of Communicable Diseases S tory of Smallpox Chickenpox Acute respiratory infections Measles German measles Influenza Diphtheria Whooping cough Meningococcal meningitis Hemophilus influenza meningitis Points on RNTCP treatment T uber culosis and HIV 2 0 . Epidemiology of Noncommunicable Diseases and Accidents T yphoid fever Acute diarrheal diseases Cholera V iral hepatitis Poliomyelitis Dracunculiasis Amoebiasis Giardiasis 21. Soil Borne Diseases Ascariasis Ancylostomiasis T etanus 22.

Infectious Disease Epidemiology 18 COMMONLY USED TERMS Infection: Means successful entry , development and / or multiplication of the organisms (pathogenic) in the body of a living being (human or animal). Such an infection may or may not lead to the development of a disease. Infectious disease: Disease resulting from an infection. Clinical infection: Infection in a dose as to result in a disease. Subclinical infection: Infection in a dose not sufficient to result in a disease. An individual with a subclinical infection may or may not transmit the disease to others. It is also called inapparent infection. Such persons are responsible for the endemicity of disease. Identification of such an individual is not possible unless laboratory investigations are done. Colonization: The infection resulting in the constitution of the normal flora of the tissue or organ. Colonization is non-pathogenic, i.e. Staphylococci in the skin and nasopharynx. Latent infection: A subclinical infection flaring-up into an active clinical disease, when the host defence breaks down. For example: V aricella virus of Chickenpox later flares up into Herpes-zoster; Flaring up of tuberculosis following measles etc. Mixed infection: Infection caused by more than one type of pathogens. Primary infection: Infection occurring in an individual, who is not having any other infection. Secondary infection: Infection occurring in an individual, who is already having an infection of another nature. C r oss infection: An infection spreading from person to person, animal to animal, animal to person or vice versa. T erminal infection: An infection occurring towards the end of the disease (usually a chronic disease) and often results in death. Endogenous infection: The normal non-pathogenic flora of the body , when assume the pathogenic character and result in a disease. Droplet infection: Infection acquired through the inhalation of droplets or erosols of saliva or sputum containing the pathogens, expelled during sneezing, coughing, laughing or talking by someone, harboring the pathogen. Nosocomial infection: An infection acquired by a patient during the stay in the hospital, either from the hospital staff, or from other patients or from hospital procedures. For example: Urinary infection following catheterization. Hepatitis B following injection or blood transfusion. Oppor tunistic infection: An infection caused by those organisms which take the opportunity provided by the host due to breakdown of the immune mechanism, resulting in a disease. It is common in AIDS. The opportunistic or ganisms are Mycobacterium tuber culosis , Cytomegaloviru s , Pneumocystitis carnii , Herpes virus, T oxoplasma gondii , Cryptococci etc. Infestation: The lodgement, growth, development and reproduction of the parasites, either on the surface of the host (like louse, ticks, mites) or inside the body of the host (like helminths). These parasites are respectively called as Ecto and Endo parasites. Contamination: Presence of infectious organism on the surface of the inanimate objects like clothes, utensils, furnitures, instruments, vehicles of transmission (like water , milk, food, blood etc) and makes it impure. Pollution: Presence of offensive matter in the environment. For example, Air pollution.

Epidemiology of Communicable Diseases 19 ST OR Y OF SMALLPOX (VARIOLA MAJOR) (OBITUAR Y) Small pox was an acute, highly infectious, exanthematous, major killer disease of children, caused by variola virus, transmitted by droplet infection, often occuring in epidemics, clinically characterised by sudden onset of high fever , severe prodromal symptoms, followed by appearance of rashes on 3rd day , centrifugal in distribution, passing through the successive stages of mucule, papule, vessicle, pustule and scab formation, leaving behind deep seated, pock marks permanently , with a case fatality rate, varying from 20 to 50 percent. In the early part of 20th century , small pox was world wide in distribution. By systematic vaccination and re- vaccination, it was eliminated from W estern countries in the first half of the century . In 1962, Govt. of India launched National Small pox Eradication Program. Till 1967, it was endemic in Africa, Asia and Indonesia. In 1967, WHO began an intensefied Global Smallpox Eradication Program by intensive surveillance, systematic vaccination and re- vaccination. As a result, country after country achieved Smallpox free status. In 1975, Govt of India further intensified the program under the banner Operation Smallpox - T a r get Zero. W ithin few months, the disease was eliminated. The last indigenous case in India occurred on 17th May 1975 in Bihar State. (Pachera village of Katihar district). On 24th May 1975, another case was reported, but was imported from Bangla Desh. The patient was a woman of 30 years old, namely Saiban Bibi, who got infected in Bangla Desh but developed fever with rashes while living on the platform of Karimganj railway station, in Assam. Since then no cases were reported from India. After an arbitrary period of two years of intensive surveillance all over India, when not even a single case was detected, India was declared Smallpox free country in April 1977 by the International Commission. W orld s last historic case of Smallpox, was reported from Somalia of Africa, on 26th October 1977. The world was declared as Smallpox-free by WHO on 8th May 1980. It was a very great achievement to eradicate smallpox and indeed a historic milestone in the history of medicine. The credit goes to the great Edward Jenner, who discovered the vaccine against Smallpox. He made a very observation that on attack of cowpox protected a milk maid, namely Sarah Nelmes against smallpox. Later , he proved his observation by taking the cowpox matter from the lesions of the milkmaid and vaccinated James Phipps, who got protected from smallpox. Edward Jenner got FRS (Fellow of Royal College of Society) for his discovery . Since the vaccinia-virus (cowpox virus) was employed to protect against variola-virus (Smallpox), the procedure was called as vaccination. By 1982, all countries officially discontinued compulsory vaccination, so much so the vaccination against small pox is considered as medical malpractice. Even though small pox has been eradicated from the world, viruses are being maintained in living conditions only in two laboratories namely US laboratory in Atlanta, Geor gia and V iral Research Institute, Moscow . This is because there are many animal pox viruses, specially monkey pox virus, which can affect human beings and it is not known whether these animal pox viruses, such as monkey-pox, tana-pox, cow-pox, camel-pox, rabbit-pox, mouse-pox, buffalo-pox, sheep-pox, goat-pox, etc. can someday replace the eradicated smallpox virus. The epidemiological factors, which favoured the eradication of smallpox are: Absence of animal reservoir . Absence of sub-clinical cases.

TYPHOID FEVER It is an acute infectious disease of the small intestine, caused by Salmonella typhi , transmitted through fecal contaminated water , food and vegetables, usually af fecting the school children. Clinically , it is characterized by continuous fever for prolonged period, severe prodromal symptoms and involvement of lymphoid tissues. W ith the availability of the antibiotics, case fatality rate is reduced to 10 percent. The term Enteric fever includes both typhoid and para- typhoid fevers. Para-typhoid fever is caused by Salm para- typhi A and B. Unless otherwise specified, enteric fever always means typhoid fever . Para-typhoid is less severe. Milestones In 1829, Louis distinguished typhoid from typhus fever . In 1839, Schonlein showed by post-mortem studies that the lesions in the Peyer s patches and mesenteric lymph nodes were specific in typhoid fever and not in typhus fever . In 1856, Budd pointed out that the disease is transmitted through the excreta of the patients. In 1880, Eberth saw the organisms in the lymphoid tissues. In 1884, Gaffky successfully grew it in pure culture. In 1890, Pfeif fer , Kolle and W right independently performed the vaccination experiments. In 1975, Germanier and Furer developed live, oral vaccine against typhoid. Magnitude of the Problem In 20th century beginning, typhoid was a global problem. In the latter half of the century , with the improvement of quality of life and socio-economic conditions, specially with reference to protected water supply , disposal of sewage and improvement in the sanitation, there has been a tremendous decline in all the developed countries, whereas in the developing countries it continues to be unabated. In India, tyhphoid is still an endemic disease, often giving rise to epidemics. It is 5th most common communicable disease. It has a huge socioeconomic impact on the country , because typhoid patients require several weeks to several months to recover and resume work. The incidence rate is about 100 to 200 cases per lakh population with CFR of 10 percent in untreated cases. Presence of typhoid is the barometer of the sanitation of the country or community . Agent Factors Causative Agent The etiological agent is Salmonella typhi . It is a gram negative bacilli, capsulated, flagellated, actively motile organism. (Exception : S. gallinarum and S. pullorum are non-flagellated and hence non-motile organisms). The organisms posses three types of antigens, namely somatic or O antigen, (specific for the group), Flagellar or H antigen (specific for the type), and capsular or V i antigen, related to the virulence of the or ganism. Antibodies to O antigen is usually higher in cases of typhoid, antibodies to V i antigen among carriers and antibodies to H antigen among immunized persons. There are about 80 types of phage types. Phage typing has proved an useful epidemiological tool in tracing the source of epidemics. The organisms are sensitive to heat and chemicals.