Public Health Questions and Answers

What do you understand by the term screening?

Screening denotes the search for unrecognized disease or defect in apparently (or outwardly)healthy persons by the application of rapid diagnostic tests, examinations or procedures. The basic objective of screening is to facilitate an early diagnosis so that the prognosis can be improved by remedial action.

 

What is mass screening?

When all members of a population are screened for disease it is called mass screening. This is very costly and the yield of cases is usually too small to warrant such a screening procedure.

 

What is high-risk screening?

High risk or selective screening refers to the situation where tests are offered only to those individuals who are at high risk of developing a specific disease. This makes the screening process more focused and reduces the overall costs as a large number of people who have extremely remote chances of developing a disease are not screened.

 

What criteria should you look for before screening for any disease?

  1. The following criteria should be satisfied before embarking on screening:
  2. The condition should be an important public health problem.
  3. The natural history of the condition from the latent to manifest disease should be adequately understood.
  4. There should be a recognizable latent or early asymptomatic stage of the disease, during which identification will lead to improved prognosis or outcome.
  5. There should be an accepted and effective treatment for the patients with recognized disease.
  6. Facilities for full diagnostic work-up and treatment should be available.
  7. There should be a suitable test available which should be valid.
  8. The test should be acceptable both to the public as well as the professionals.
  9. There should be an agreed policy on whom to treat as patients, including the management of borderline disease.
  10. Case finding should be a continuous process.
  11. The cost of early diagnosis and treatment should be economically balanced in relation to the total expenditure on medical care (The opportunity cost should be justifiable).

These can be classified as:

  • Disease criteria
  • Test criteria
  • Diagnostic and treatment infrastructure criteria

 

What is sensitivity?

This refers to the proportion of truly diseased individuals in the population who have been correctly identified as diseased by the screening test. A test with a high sensitivity gives only a few false negatives.

 

What is specificity?

This refers to the proportion of the normal individuals who are correctly labeled as nondiseased by the screening test. A test with a high specificity will only give a few false positives. It is desirable that a screening test should have a high sensitivity and specificity.

 

What are the different ways in which communicable diseases can be transmitted?

  1. Communicable disease can be transmitted in a number of ways:
  2. Direct transmission: Contact transmission
  3. Indirect transmission: Vehicle (fomite) borne, vector-borne, air-borne (droplet nuclei and infected dust)
  4. Transplacental

 

What is the period of communicability?

Period of communicability or communicable period rfers to the time during which an infectious agent may be transferred directly or indirectly from an infected person to a susceptible person. This period is usually equal to the maximum known incubation period for that disease.

 

What is contact transmission?

When disease is spread by direct contact with an infected person, it is called contact transmission. This may be by kissing, touching, biting or sexual intercourse. Ringworm, scabies, yaws, etc. are examples of such diseases.

 

What are zoonoses?

An infectious disease transmissible under natural conditions from vertebrate animals to man is called a zoonoses. There are over 150 disease common to man and animals. These include anthrax, psittacosis, liver fluke, T. solium, T. saginnata, bovine TB, salmonellosis, brucellosis, scabies, plague, typhus, yellow fever and KFD.

 

What is passive immunization?

Passive immunization refers to the injection of specific protective antibodies (hyper immune serum, immune serum globulin, etc.) to provide immediate protection to an individual. Transplacental transfer is also an example of passive immunization. Here, readymade antibodies are provided to an individual especially in an emergency when one cannot wait for the body to produce antibodies. Examples are diphtheria, tetanus, and rabies, etc.

 

What is active immunization?

In active immunization, a live/killed vaccine is injected and the body reacts by producing antibodies, which make the individual immune and protect against attack by infectious agents. Active immunity is also achieved after suffering from a disease like measles, chickenpox, etc. Active immunity is long lasting and more effective in preventing future disease. The only drawback is that it takes time for the body to produce antibodies and therefore active immunization is usually not useful in an emergency. Rabies is an exception because the incubation period of the disease is long.

 

What is the incubation period for chickenpox?

Incubation period is 7-21 days and commonly it is 14-16 days.

 

How does chickenpox spread?

It can affect people of all ages but most commonly children below 10 years are affected as they do not have protective antibodies. It is most commonly spread due to respiratory secretions from infected persons, which are teeming with the virus. Crusts of chickenpox are not infective.

 

What is the incubation period for measles?

The incubation period of measles ranges from 8 –16 days with an average incubation period of 10 days.

 

What are the different life threatening complications of measles?

Common life-threatening complications of measles include broncho-pneumonia and diarrhea. Encephalitis can also occur rarely.

 

When is measles most infectious?

Measles is most infectious 4 days before to 5 days after the rash appears.

 

How does the rash of measles differ from the rash of chickenpox?

An eruptive rash appears in measles as dark red macules or maculopapular granules, first evident behind the ears and at the junction of the scalp and forehead and then spreading over the face, trunk and limbs, very rapidly. The rash lasts for 4-6 days and disappears in the same order in which it appeared. It dries off leaving a brawny discoloration of the skin. The rash in chickenpox has a centripetal distribution – first appearing on the trunk and then spreading towards the periphery. The palm and soles are not affected. The rash is seen mostly on the flexor surfaces and appears on the very first day and thereafter in crops, evolving very rapidly. The lesions are superficial, unilocular and are surrounded by a red areola. They are small, elliptical and mostly discrete with no umblication.

 

What is German measles?

German measles is Rubella and is a mild eruptive fever like measles. It is caused by Rubella virus.

 

What are the complications if a pregnant mother gets Rubella?

The special public health significance of Rubella is that a child may be born with congenital defects like deafness, microcephaly, microphthalmia, PDA, septal defects and other malformations, which are called the Congenital Rubella Syndromme, if the mother is infected during pregnancy. The frequency of congenital defects is 20-25% if infection occurs in 1st trimester and less after that.

 

What is MMR vaccine and how and when should it be given?

MMR vaccine is measles, mumps and rubella vaccine, which is a live, attenuated vaccine and is administered as a single IM dose after 1 year of age. If measles vaccine has been administered to a child at 9 months, MMR should be given at 15 months of age.

 

Which diseases do you know of which are planned to be eradicated?

Gineaworm, poliomyelitis and leprosy are three major diseases, which are on the eradication agenda. Smallpox was the first disease, which was successfully eradicated.

 

 What are the diseases caused by rodents?

Plague, murine typhus, salmonellosis, Weil’s disease, rate bite fever, trichinosis, rickettsial pox and lymphocytic choriomeningitis are diseases caused by rodents.

 

How can you distinguish Culex from Anopheles mosquitoes?

The anopheles lays eggs singly on water while culex lays eggs in clusters or rafts of 100-200 eggs. Culex eggs are oval with no air floats while anopheles eggs are boat shaped with lateral air floats. The larvae of anopheles have no siphon tubes, lie parallel to water surface and have palmate hair on abdominal segments, while in culex, two siphon tubes are present, they hang at an angle and have no palmate hair. Adult anopheles sit against the wall at an angle, have spotted wings and palpi are long while adult culex sit parallel to the wall and the head and body are angled or hunch backed, make ringing noises in ears, have no spots on wings and the palpi are shorter in the females.

 

What are the common diseases transmitted by mosquitoes in India?

The common diseases transmitted by mosquitoes in India are malaria (anopheles), filarial, JE and West Nile fever (Culex), Malayan filariasis and Chikungunya fever (Mansonia) and dengue, yellow fever, DHF and Chikunganya fever (Aedes).

 

What advice on chemoprophylaxis for malaria will you give to a foreigner visiting India?

Chloroqine 300 mg once a week starting 2 weeks before arrival or latest on the day of arrival and continued for 4-6 weeks after leaving the country is useful if there is no resistance to chloroquine in the area to which the foreigner is traveling. Sulfadoxine – pyremathamine combination or mefloquine can also be taken if chloroqine resistance is reported.

 

What is presumptive treatment?

This refers to treating every case of fever presuming it to be malaria and therefore it is called presumptive treatment. This consists of 600 mg (4 tablets) of chloroquine given to a febrile person without waiting for the report of the blood smear.

 

What are Fever Treatment Depots?

These are the health facilities where personnel collect the blood smear and provide presumptive treatment to the febrile individuals. If the smear is positive, the health personnel go back and provide radical Rx.

 

What drugs and how much will you give for radical treatment of P. falciparam malaria?

Radical treatment consists of a single dose of 600 mg chloroquine plus 45 mg of primaquine.

 

What are impregnated nets?

These nets are used for control of malaria and are plastic nets, which are impregnated with synthetic insecticides.

 

What are the different plasmodium species causing malaria in India?

The species in India are vivax, falciparum and malariae.

 

What is spleen rate in malaria?

Children aged 2 – 10 years are examined for enlargement of spleen and areas are classified according to endemicty as indicated by the spleen rate :

Below 10% – Non endemic

10 – 25% – Hypoendemic

25 – 40% – Endemic

> 40% – Hyper endemic.

 

What are the indices for blood surveys for malaria?

The main indices are:

  1. Infant parasite rate: It is a good indicator of recent infection and is measured by proportion of blood smears of infants positive for malarial parasite.
  2. Children parasite rate: Here blood smears of children aged 2-10 years are examined.
  3. Annual parasite index: This is the most common index used currently. It is defined as the numberof confirmed malaria cases per 1000 persons in an area per year.
  4. Slide positivity rate: Proportion of slides examined which are positive for the malarial parasite.
  5. Slide falciparum rate: Proportion of slides examined which are positive for falciparum species.
  6. Annual Blood Examination Rate: The number of blood slides examined per 100 population. An ABER of 10% is warranted for good coverage of the population under surveillance.
  7. Monthly blood examination rate: This should be 1%during the non-transmission season and 2% during the transmission season (July – Oct) in areas under active surveillance and 15% and 20% respectively (as a proportion of new OPD cases) in passive surveillance zones.

 

What is active surveillance?

In active surveillance, the health worker goes from house to house to search for cases of fever.

One round is completed in a fortnight and the worker then repeats the visits. Thus every house is visited every fortnight. The health worker asks 4 questions:

  1. Is anybody suffering from fever currently?
  2. Did anybody suffer from fever in the pastfortnight?
  3. Did any guest with fever come to the house in the past fortnight?
  4. Did any fever case leave the area in the past fortnight?

Any person complaining of fever is then given presumptive treatment after collecting a blood smear.

 

What is passive surveillance?

In passive surveillance, any fever case reporting to a health facility is given presumptive treatment after a blood smear is made.

 

What is Annual Parasite Incidence and how is it important?

It is defined as the number of confirmed malaria cases per 1000 persons in an area per year. It is the most sensitive index in use currently. The target for 2000 AD was an API of 0.5% which was more than 2 in 1991.

 

What is the objective of the modified plan of operations in malaria?

The objectives of the modified plan of operations are:

  1. To prevent deaths
  2. To reduce case load
  3. To consolidate achievements made under NMEP
  4. To maintain the green and industrial revolution.

 

 What is Annual Blood Examination Rate?

This is a monitoring tool to ensure that adequate number of blood slides have been collected. The workers should have collected blood smears eqivalent to > 10% of the population residing in an area. This is based on the expectedload of fever cases in a community in a year.

 

Which are the endemic areas for chloroquine resistant malaria in India?

All the North East States in the country, parts of Chttisgarh, Madhya Pradesh, Andhra Pradesh, Jharkhand, West Bengal and Orissa are endemic areas for chloroquine resistant malaria.

 

Name some arthropods which transmit diseases.

Arthropods, which transmit disease, include mosquitoes, houseflies, sand fly, tsetse fly, black fly, lice, rat flea, reduviid bug, cockroaches, ticks, trombiculid mite and cyclops.

 

What do you understand by biological control?

Biological control means use of animal species to kill disease causing vectors. Gambusia and Lebistes fish have been used effectively in malaria control. Coelomomyces fungus and some other fungi, bacilli, protozoa and nematodes have been tried for biological conrol. This method, if effective can reduce the harm caused to man and environment by insecticides.

 

What are the diseases transmitted by lice?

Epidemic typhus, quintana, trench fever, relapsing fever and secondary dermatitis are some disease caused by lice.

 

What are arboviruses?

They are defined as those viruses that are maintained in nature principally or to an important extent through biological transmission between susceptible vertebrate hosts by haematophagus (blood feeding) arthropods. More than a 100 arboviruses are known to produce disease in man.

 

What diseases are transmitted by hard tick?

Hard ticks transmit tick typhus, viral encephalitis, KFD, tularemia, tick paralysis and babesiosis.

 

What diseases are transmitted by soft tick?

The soft ticks transmit Q fever and relapsing fever.

 

How is Diphtheria spread?

Diphtheria is spread through direct droplet/ direct air-borne routes and indirectly through inhalation of contaminated dust by dried particles of the diphtheria membrane. It can also be spread through contaminated milk, fomites, convalescent or healthy carriers, cross infection in wards & infection of wounds or cuts in skin or mucous membrane, including conjunctiva.

 

What is the Schick test?

The Schick test was done to identify individuals whoare susceptible to diphtheria and those who are allergic to the toxoid use in the vaccine. With universal immunization becoming the rule, the use of the test has decreased tremendously. The test was done by intradermal injection of 0.2 ml of Schick test antigen or toxin in one forearm and heated toxin in the other forearm as a control.

 

Which strain is used for making BCG vaccine?

The Danish 1331 strain of the BCG antigen has been recommended by the WHO for production of BCG vaccine.

 

How is BCG vaccine given?

0.1 ml of BCG vaccine (producing a weal of 8 mm) is given intradermally over the deltoid muscle using a tuberculin syringe. In neonates below 4 weeks of age, 0.05 ml is recommended. The dose is given immediately after birth or as soon as possible after birth, preferably before 6 weeks of age.

 

What are the normal reactions that occur after giving BCG vaccine and what advice should be given to the mother?

The weal raised immediately after giving the BCG vaccine disappears within a few hours. Nothing happens over the next two weeks. Redness and induration at the site are seen in the third week. A papule then develops reaching its maximum size in the 4th week. The papule cracks,discharges pus and is gradually changed into a crust during the 5th – 6th week. The scab falls off during the 7th – 8th week leaving a small oozing ulcr which heals and leaves a scar about 5mm in diameter. These reactions are often more marked in positive reactors.

Mothers should be sensitized about all thenormal reactions so that they do not get worried. They should be told not to apply any medicine or lotion to the injection site when the crust forms or when pus is seen. They should be told to look for enlargement of regional lymph nodes, keloid formation or an abscess formation and to bring the child to the clinic if any such complications are seen.

 

What is the Tuberculin test?

The tuberculin test is performed to screen individuals who are already infected and those who are highly susceptible to the disease. Tuberculin containing PPD (purified protein derivative) prepared from the RT strain along with Tween 80 is injected intradermally. The injection is given on the anterior side of the forearm and the result is read after 48 – 72 hours.The induration is measured and any induration greater than 10 mm is taken as positive. Strong reactors (more than 20 mm induration) have more chance of developing active TB. Similarly weak reactors (< 5 mm) also have a higher chance of infection. In countries where BCG vaccine is given at birth, tuberculin testing loses its value.

 

What is chemoprophylaxis? Gives some examples

Chemoprphylaxis is the use of drugs to prevent onset of disease in individuals who are exposed to disease causing organisms. This can be of two types – Primary (giving drugs before a person is apparently infected) or secondary (after a person is infected but disease has not manifested). Malaria and TB are two diseases where the principles of chemoprophylaxis are put to good use.

 

What is Short Course Chemotherapy?

Short course chemotherapy is now being widelyused in TB. A combination of 4 drugs is given for the initial period followed by 2-3 drugs during the follow up phase of 4-6 months. The total duration of most short course regimens is 6- 8 months. A number of regimens have been developed. Common ones use Rifampicin, INH,Streptomycin and Pyrazinamide for 2 months followed by Rifampicin and INH for 4-6 months. The intensive phase with four drugs rapidly converts a sputum positive person to sputum negative and therefore decreases the transmission potential of the affected individual.

 

What is DOTS?

A major problem in tuberculosis is the lack of compliance with the recommended drugs by the patients and this leads to inadequate treatment, which further is responsible for multi drug resistance. To avoid this, under the National Programme, the patients are made to take the drugs in the presence of the health workers. This is therefore called Directly Observed Treatment Schedule (DOTS).

 

What is DOTS-Plus?

Because of the emergence of multiple drug resistance to drugs used as the primary line of management for TB, the WHO has embarked on a programme of directly supervised regimens using drugs where no resistance has been reported. These regimens are only to be used in areas specified as suffering from MDR TB. It is also important that the secondary drugs are not used routinely and sold across the counter in such areas to avoid the emergence of resistance to these drugs. This is called DOTS Plus.

 

What is RNTCP?

The National TB Control Programme has been revamped with the initiation of directly observed treatment regimes and an augmentation of outreach activities to increase the compliance of patients to recommended drugs. These new initiatives in the programme have resulted in the national programme now being called Revised National TB Control Programme.

 

What do you understand by defaulter action?

A patient who does not come back for drugs for one month from the due date for medicines is called as a person lost to treatment. A postcard is sent to the patient after a week of default and the patient’s home is visited if the patient still does not come back. This is called defaulter action. With short course regimens default has decreased during the initial phase of treatment.

 

Which year did the National TB Programme start? What are the main objectives and strategies under the Programme

The National TB Control Program started in 1963. It aims at systematic reduction of TB in the community within the available resources of the country, within a reasonable period of time. The short-term objective of the program is to diagnose and treat patients at places nearest to their homes and also to provide preventive services, especially in the rural areas to reduce disability and death to the extent possible. The long-term objective of the programme is to reduce the problem gradually till it ceases to be a public health problem.

 

What is the prevalence rate of tuberculosis infection in India?

The prevalence of TB infection is the percentage of individuals in the community showing positive reaction to tuberculin test. Its usefulness has decreased in recent years due to widespread BCG immunization. A third of the Indian population is infected.

What do you understand by Annual Infection Rate in TB?

This is also called the incidence of infection and tuberculin conversion index. It is the proportion of persons converting from tuberculin negative to positive in a particular year. Annual infection rate in infants and children is the best indicator of transmission of infection in a community. The prevalence rate of TB disease is 4 per 1000 population while the incidence rate of disease is 1 per 1000 population.

How many radiologically active cases and how many sputum positive Tuberculosis cases can you expect in a population of a district with 1-2 million population?

Each district is likely to have 20,000 radiologically active cases including 5000 sputum positive cases at any point in time. Annual incidence of new cases is expected to be 2000.

 

Who is labeled as a case of tuberculosis?

A case of TB is an individual who is sputum positive and is therefore capable of transmitting infection.

 

What is the difference between a cases and a suspect of TB?

A suspect is a person who is sputum negative but has radiological evidence of Tubercular shadows in the lungs.

Therefore, a case is infectious while a ‘suspect’ is not infectious.

 

What is a District TB Centre?

A district is the nerve centre for TB control activities under the NTCP. All patients are registered with the District TB Centre and drugs are provided from here. All defaulter action in addition to maintenance of the live register is the responsibility of the District TB Centre.

 

What is the danger signals signifying severe disease in Acute Respiratory Infections?

Danger signals, which signify very severe disease, are:

  1. Child stops proper feeding b. Child too sleepy or difficult to wake up c. Stridor even when the child is calm.
  2. Wheezing e. Convulsions f. Severe malnutrition g. A very young infant who has fever or is cold to touch.

 

Name some food-borne diseases and specify measures of control for these diseases?

Common food-borne diseases are cholera, typhoid, amoebiasis, bacillary dysentery, taeniasis, trichinellosis, trichuriasis, hydatid cyst & food poisoning

 

What is the incubation period of cholera?

The incubation period for cholera ranges from 1 – 5 days. Most commonly it is 12 hours to 2 days.

 

How can you differentiate cholera from food poisoning?

The following table illustrates the differential diagnosis of cholera and food oisoning:

 

 What is ORT?

Oral Rehydration Therapy is the cornerstone ofmanaging dehydration in diarrhea. It is estimated that it can save an estimated 4 million children dying from diarrhea every year. Some people differentiate between ORT and ORS. The constitution of packed physiological salts as a solution is called ORS while the preparation of home-made solutions for oral rehydration are referred to as Oral Rehydration Therapy.

The contents of the Oral Rehydration Salts solution approximate the water and electrolyte composition of diarrheal stool, which is isotonic in nature.

 

How can Oral rehydration fluid be made at home?

Home-made rehydration fluid can be made by adding sugar and salt to water. Eight heaped teaspoons of sugar and 1 level teaspoon of salt should be added to one litre of clean water. The salt and sugar should be dissolved completely.The patient should be given as much of the solution as he can take comfortably. Small sips can be repeated at frequent intervals. Once the solution is prepared it should be consumed within 24 hours and whatever is left over should be discarded and not consumed after 24 days. Fresh solution should therefore be prepared everyday.

 

What is the composition of WHO formulated ORS?

The composition of standard WHO formulated

ORS is as follows:

– Sodium chloride: 3.5 grams – Sodium bicarbonate: 2.5 grams – Potassium chloride: 1.5 grams – Glucose: 20 grams

– Water: One litre This provides: 90 meq/litre of Sodium 20 meq/ litre of Potassium 80 meq/ litre of Chloride 30 meq/ litre of Bicarbonate

ORS containing sodium bicarbonate has short shelf life in hot, humid conditions. Sodium bicarbonate reacts with glucose in the presence of dampness (water) and the powder becomes discoloured and less effective.

Therefore, replacing 2.5 grams of sodium bicarbonate with 2.9 grams of trisodium citrate increases stability of ORS and also reduces stool output.

 

How long can the ORS be used after preparation?

Once prepared, ORS should be consumed within 24 hours. After that period, whatever is left over should be discarded and fresh solution should be prepared.

 

What are the features of Salmonella food poisoning?

Salmonella food poisoning is characterized by an incubation period of 12-24 hours, abdominal pain, diarrhea, vomiting and fever. The organisms most commonly multiply rapidly in animal foods like milk and milk preparations, meat, fish, eggs, ice creams, puddings, pastries, sausages and meat pies, etc. and so history of intake of such foods is elicited.

 

What are the features of botulism?

In botulism, change of voice, diplopia, ptosis, cranial nerve palsies and obstinate constipation are observed. History of consumption of tinned food is usually observed. An incubation period of 12-36 hours is seen. Death usually occurs in 3- 7 days and mortality is high (40%).

 

Who is labeled as a convalescent carrier?

A convalescent carrier is one who sheds infective micro-organisms during the period of convalescence. In typhoid this is for a period of 1-2 weeks after the temperature comes down.

 

Who is called a permanent carrier?

A permanent carrier is one who continues to shed organisms forever after the disease has been cured. This is seen in typhoid where the gall bladder and kidneys are involved and bacilli are passed for a long time with interspersed periods of remission. 2.5% of typhoid cases develop into permanent carriers.

 

What is the incubation period of Typhoid?

The commonly observed incubation period of typhoid is 10 – 14 days, but it can range from 4 – 21 days.

 

What vaccines are used for active immunization against Typhoid?

A number of vaccines are used for active immunization against typhoid. These include:

– TAB vaccine – AKD vaccine – Bivalent vaccines containing S. typhi and S. paratyphi

– Live attenuated oral vaccine (Ty 21a)

TAB vaccine is the earliest vaccine developed and was introduced in 1896.Live vaccines are now routinely used and are very effective and have less side effects compared to the killed vaccines.

 

How many doses of oral typhoid vaccine are given for primary immunization?

A single dose of oral vaccine provides long-term immunity. Booster doses should be given every 5 years.

 

When should booster of acetone killed typhoid vaccine be given?

Booster doses should be given every 3-5 years.

 

What advice should you give to a person who is being given AKD typhoid vaccine?

A person given AKD vaccine should not indulge in hard physical work on the day of injection as this may lead to more adverse reactions. Fever, myalgia and rash at the injection site are commonly seen. The myalgia can be debilitating and if the whole family is immunized at the same time, there may be nobody fit to cook for that night!! All these reactions are transient and go away within 24-36 hours.

 

Who is the reservoir of infection in Amoebiasis?

Man is the reservoir of infection in Amoebiasis.

 

What is the difference in incubation period of hepatitis A and hepatitis B?

The incubation period for hepatitis A is 15-50 days while it is 50-150 days for hepatitis B.

 

What is surface antigen and how is it useful?

The surface antigen in hepatitis B (HBsAg) can be detected in blood for several weeks before theonset of symptoms and persists for weeks or months. Its continued presence indicates a chronic infection.

 

How is hepatitis B transmitted? How does this differ from other hepatitis causing viruses?

Hepatitis B is transmitted through body fluids including blood and through sex where exchange of body fluids takes place. The routes of transmission can be categorized as follows:

– Parenteral or percutaneous: Through infected blood, blood products, syringes, transfusion apparatus, etc.

– Vertical or perinatal spread: Mother to infant transmission can occur when the mother is a chronic carrier or suffers from acute infection during the first trimester of pregnancy. The infection can also occur during passage through the birth canal or during the post-natal period due to close contact.

– Permucosal spread: Blood, saliva, vaginal fluids and semen are infective.

What is the incubation period of polio?

The common incubation period is 7-14 days with an overall range of 3-35 days.

 

How is the prevalence of polio estimated in the community?

The prevalence of polio in the community is assessed by conducting lameness surveys in the community among

children aged 0-10 years. Lameness in children aged 0-4 years is most indicative of the current level of the problem.

 

What are the different types of vaccines available for polio?

There are two types of vaccines available for prevention against polio – One is a killed vaccine and is injected (Salk vaccine) and the other is an live vaccine which is given orally (Sabin vaccine).

 

What is Pulse Polio programme?

The pulse polio programme is an initiative for eradication of polio from all the endemic areas. Under this programe, in addition to the routine

 

What is the Lepromin Test?

This test detects cell mediated immunity. It simply measures the individual susceptibility or resistance. It does not indicate past or presentinfection. Lepromin positivity is associated with resistance to leprosy infection. After intrademal injection of 0.1 ml of lepromin antigen, two types of reactions can be seen. These are referred to as the early (Fernandez), which is read at 48 hours and the late (Mitsuda) reaction, which is read at 21 days. The early reaction comprises of redness and induration and is regarded as positive if the area of redness is greater than 10 mm at 48 hours.

The late reaction consists of a papule or nodule, which is first measured after 2 weeks, and then at weekly intervals.

 

What is the Indian classification of Leprosy?

In the classification, leprosy is categorized into one of five categories. These are

indeterminate leprosy, tuberculoid leprosy, pure neuritic, border-line lepromatous and lepromatous. The first three categories fall under paucibacillary leprosy while the last two fall under multi-bacillary leprosy.

 

What is the rationale for MDT in Leprosy?

MDT in leprosy is very useful because of the

following reasons:

  1. To interrupt transmission of the infection in the community as rapidly as possible using a combination of bactericidal drugs.
  2. It provides an opportunity for cure
  3. It helps to prevent drug resistance.
  4. A shorter course of therapy ensures a better compliance
  5. There is reduced work load on the health-care delivery system.

 

What is paucibacillary leprosy?

In this type of leprosy, there are few bacilli in the skin wounds and secretions and therefore such cases are of low infectivity.

 

What is multibacillary leprosy?

In multibacillary leprosy, the secretions and wounds are teeming with bacilli and these patients are therefore very infectious. Lesions in these patients progress much faster.

 

What is bacteriological index?

This index denotes change in the number of leprosy bacilli present in the tissues. Smears are made from at least 7 sites, including a nasal smear, both earlobes and 4 skin lesions. Each smear is graded separately. If there are no bacilli, a score of ‘0’ is given while if bacilli are found in some fields (mean < 1 bacilli per field), it is scored as ‘1’; If bacilli are found in all fields it is scored as ‘2’ and if many bacilli are found in all fields it is scored as ‘3’. All scores of all smears are added and a mean calculated. If the index is < 2, it is paucibacillary leprosy and if it is > 2 it is classified as multibacillary leprosy.

 

What is morphological index?

This index is the percentage of solid rods among 200 organisms counted in a smear stained for demonstrating M. leprae. Solid rods represent the viable bacilli. This index changes more rapidly than the bacteriological Index. If it shows a rise after an initial decline, it could indicate either inadequate drug intake or development of drug resistance.

 

What is the recommended treatment for multibacillary leprosy?

The regimen recommended by WHO consists of the following:

– Rifampicin: 600 mg once every week as a supervised dose.

– Clofazimine: 300 mg once every 4 weeks under supervision + an unsupervised dose of 50 mg daily.

– Dapsone: 100 mg unsupervised every day.

Treatment s continues for a minimum of 2 years and until the smears become negative after that.

 

What are leprosy control units?

These are established in endemic zones with a prevalence rate of 5 per 1000 and above and cover a rural population.

 

What are SET centers under NLEP and what are their functions?

SET stands for survey, education and training and these are the main functions of these centers. These are established in endemic zones where prevalence rate is < 5 per 1000. Leprosy paramedical workers trained in physiotherapy, health education and treatment are posted in these centers and they function under the MO in charge of the PHC. The functions of these centers are:

Detection of early cases based on a house-tohouse survey.

Health education

Free treatment of all cases

Contact tracing

Chemoprophylaxis of contacts

 

 What are STDs?

STDs are diseases in which sex plays an important part in transmission. They include the five classical diseases–syphilis, gonorrhea, chancroid,LGV and granuloma inguinale and additional conditions like non gonococcal urtheritis, herpes progenitalis, genital warts, trichomoniasis and moniliasis. In addition, some diseases where sexual transmission is possible but not epidemiologically important are also considered as STDs. These include genital scabies, hepatitis B, genital pediculosis and genital molluscum contagisum.

 

What is the incubation period of gonorrhea and how is the disease spread?

The incubation period of gonorrhea is 2-7 days. It is primarily spread by sexual intercourse. The chance of contracting gonorrhea after a single exposure is 20-35% for men and probably double for women.

 

How is filariasis transmitted?

Mosquito bites are the principal mode of transmission of filariasis. Transmission is remarkably inefficient. In an endemic area, about 100,000 mosquito bites are required annually to produce one new case of filariasis.

 

How can an epidemic of dengue fever be controlled?

Mosquito control measures aimed at preventing breeding, killing of larvae and adults and avoiding mosquito bites is essential. The infected person should be confined to the house and kept in a mosquito net if possible to prevent transmission of infection during the first five days when the person is infective. Health education to protect themselves against mosquito bites is important.

 

What species are the primary hosts in Japanese encephalitis?

Pigs and birds are primary hosts of Japanese encephalitis. The infection in man is a dead end infection.

 

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