Infectious Diseases Practice Questions

Q: What is the recommended period of isolation for a suspected case of diphtheria?

14 days. ***14 days*** - Isolation for suspected diphtheria cases should continue for **14 days** or until **two consecutive negative cultures** (taken at least 24 hours apart) are obtained after completing antibiotic therapy. - The standard antibiotic course for diphtheria is **14 days** (erythromycin or penicillin), and patients remain potentially infectious throughout this period. - This ensures complete eradication of **Corynebacterium diphtheriae** from the respiratory tract and prevents secondary transmission. *7 days* - A 7-day isolation period is **insufficient** for diphtheria management as the standard antibiotic treatment duration is 14 days. - Patients may still harbor viable organisms and remain infectious after only 7 days of treatment. - Premature discontinuation of isolation increases the risk of **disease transmission** in the community. *10 days* - While 10 days is longer than 7 days, it still falls **short of the recommended duration** for complete antibiotic therapy and bacteriological clearance. - Standard guidelines require either completion of **14 days of antibiotics** or documented negative cultures before ending isolation. *12 days* - A 12-day isolation period is **not adequate** as it does not align with the standard 14-day antibiotic treatment protocol for diphtheria. - Isolation should be maintained until the full course of antimicrobial therapy is completed and cultures confirm clearance.

Q: To prevent KFD which of the following is not used?

Deforestation. ***Deforestation*** - **Deforestation** is not a method used to prevent Kyasanur Forest Disease (KFD); in fact, it can disrupt ecosystems and potentially alter disease transmission patterns in unpredictable ways. - Preventing KFD primarily focuses on reducing human exposure to **infected ticks** and managing the disease in its natural reservoirs. *Self protection against ticks* - **Self-protection** against ticks is crucial, as KFD is primarily transmitted through the bite of infected ticks. - Measures include wearing protective clothing, using **insect repellents**, and avoiding tick-infested areas. *Control of cattle roaming in the forest* - **Controlling livestock** such as cattle in forested areas can help prevent KFD by limiting the movement of host animals for ticks, which are vectors for the disease. - This reduces the likelihood of infected ticks being carried into human settlements or increasing tick populations in areas frequented by humans. *Vaccination* - **Vaccination** is an effective preventive measure against KFD, particularly for individuals living in or visiting endemic areas. - The vaccine provides protection by inducing an **immune response** against the **Kyasanur Forest Disease virus**.

Q: True about epidemiology of cholera-

Food can transmit the disease. ***Food can transmit the disease*** - Cholera is commonly transmitted through the **fecal-oral route**, and **contaminated food** is a significant vehicle for this transmission. - Food can become contaminated when handled by infected individuals or prepared with **contaminated water**. *Boiling water cannot destroy the organism* - **Boiling water** for at least one minute is a highly effective method for killing Vibrio cholerae, the bacterium responsible for cholera. - High temperatures denature proteins and disrupt the cellular structure of the bacteria, rendering it inactive. *Vaccination gives 90% protection* - Oral cholera vaccines typically provide **modest protection**, ranging from 50% to 85% for a limited duration, usually around 2-5 years. - No vaccine offers 90% protection against cholera, and protection wanes over time, necessitating booster doses or revaccination. *Cholera cannot be transmitted by contaminated water* - **Contaminated water** is the primary mode of cholera transmission. - Drinking water contaminated with **Vibrio cholerae**, often from feces of infected individuals, is the most common cause of outbreaks.

Q: All are zoonotic disease except -

Scabies. ***Scabies*** - **Scabies** is a parasitic skin infestation caused by the **Sarcoptes scabiei mite**, which typically spreads from person to person through direct skin contact. - While animal scabies exists, human scabies is primarily a **human-to-human transmission** disease and is not generally considered a zoonosis in the context of common human infections. *Leptospirosis* - **Leptospirosis** is a bacterial disease transmitted through contact with urine from infected animals or contaminated water/soil. - It is a classic example of a **zoonotic disease** affecting a wide range of mammals, including rodents, livestock, and pets. *Rabies* - **Rabies** is a viral disease primarily transmitted to humans through the bite of an infected animal, usually a mammal. - It is a well-known and fatal **zoonotic disease** worldwide, with dogs being the most common source of human infection in many regions. *Brucellosis* - **Brucellosis** is a bacterial infection transmitted to humans through contact with infected animals (e.g., cattle, goats, sheep) or consumption of contaminated unpasteurized dairy products. - It is a prominent **zoonotic disease** resulting in fever, sweating, and weakness, among other symptoms.

Q: Maximum consumption of antibiotics occurs for:

Animal non-therapeutic use. ***Animal non-therapeutic use*** - Globally, a **significant portion of antibiotics** is used in **livestock** for **growth promotion** and **disease prophylaxis** rather than treating active infections. - Estimates suggest that **50-70% of global antibiotic production** has historically been used in animal agriculture, with a substantial fraction for non-therapeutic purposes. - This widespread use contributes significantly to the development of **antimicrobial resistance (AMR)**, a critical public health concern. - Note: Recent regulations in many countries (EU, USA) have restricted growth promotion use, but globally this remains a major consumption category. *Human non-therapeutic use* - This includes non-prescription use, inappropriate prescribing, and self-medication by humans. - While this contributes to resistance issues, it represents a **smaller proportion** of total global antibiotic consumption compared to agricultural use. - This is a growing concern in low- and middle-income countries with weak prescription regulations. *Human therapeutic use* - Antibiotics are essential for treating **bacterial infections in humans** and represent a significant area of consumption. - Human therapeutic use accounts for approximately **20-30% of global antibiotic consumption**. - This proportion has been increasing, particularly after the COVID-19 pandemic due to secondary bacterial infections. *Animal therapeutic use* - Antibiotics used to treat active **bacterial infections in animals** (veterinary medicine). - While necessary for animal health and welfare, this use is **less than non-therapeutic applications** such as growth promotion and mass prophylaxis in intensive farming systems.

Q: Mycobacterium tuberculosis infection in human is most commonly because of -

Inhalation. ***Inhalation*** - **Inhalation of aerosolized droplets** containing *Mycobacterium tuberculosis* is the primary mode of transmission. - These droplets are expelled when infected individuals **cough, sneeze, or speak**. - Accounts for **>95% of TB cases** worldwide. *Ingestion* - **Ingestion** of contaminated food or milk (particularly unpasteurized milk from cattle with *M. bovis*) can cause TB. - Results in **gastrointestinal or oropharyngeal TB**, which is much less common than pulmonary TB. - Now rare due to **pasteurization** and cattle testing programs. *Inoculation* - **Inoculation** typically refers to the direct introduction of the pathogen through skin breaks or medical procedures. - While possible in specific scenarios (e.g., laboratory accidents, contaminated needles), it is **not the most common route** for widespread human infection. *Contact* - **Direct contact** with an infected person (e.g., skin-to-skin touch) is generally not an effective way to transmit *Mycobacterium tuberculosis*. - The primary route requires the pathogen to be **airborne and inhaled** deep into the lungs.

Q: A boy got an unprovoked bite from a neighbour's dog. The animal control authority caught the dog and it was found to be healthy. What is the most appropriate next step in the management of the dog?

Observe the dog for 10 days for signs of rabies. ***Observe the dog for 10 days for signs of rabies*** - According to **WHO and ICDCDR guidelines**, when a biting domestic dog/cat is captured and appears healthy, the standard protocol is to **observe the animal for 10 days** for signs of rabies. - If the dog remains **healthy throughout the 10-day observation period**, it confirms that rabies virus was not present in its saliva at the time of bite — the rabies virus appears in saliva only **2–3 days before clinical signs develop**. - During this observation window, **post-exposure prophylaxis (PEP) for the patient** may be initiated and can be discontinued if the animal remains healthy, or withheld pending results, depending on local protocols. *Test antibody level in the dog* - **Antibody testing** does not determine whether the animal is currently **shedding rabies virus in saliva**, which is the key factor for transmission risk. - Antibodies may reflect **prior vaccination** and cannot indicate active infection or current infectivity — irrelevant for immediate post-bite animal management. *Perform euthanasia for the dog* - **Euthanasia and brain examination** is reserved for animals showing **clinical signs of rabies**, those unavailable for observation, or when **confinement is not feasible** (e.g., wild animals, unowned strays). - Since the dog is **healthy and available for observation**, euthanasia is not indicated and would be unnecessary and unethical. *Start post-exposure prophylaxis* - **Human PEP** addresses the **patient's management**, not the animal's. This question specifically asks about the next step in managing the dog. - PEP for the boy is a concurrent consideration (especially for Category II/III unprovoked bites), but the decision regarding the animal is to observe it for 10 days, which in turn informs whether PEP can be discontinued or needs continuation.

Q: Species of Anopheles causing malaria in Andaman & Nicobar island?

Anopheles epiroticus. ***Anopheles epiroticus (formerly Anopheles sundaicus)*** - **Anopheles epiroticus** is the **primary malaria vector in the Andaman & Nicobar Islands**. - It belongs to the **Anopheles sundaicus complex** and is highly adapted to **coastal and island ecosystems**. - It breeds in **brackish water** and is an efficient vector for both **Plasmodium falciparum** and **Plasmodium vivax**. - This species is characteristic of **coastal Southeast Asia** and island territories. *Anopheles dirus* - **Anopheles dirus** is a primary vector in **forest-fringed areas** of mainland Southeast Asia and northeastern India. - While it is an efficient malaria vector, it is **not the predominant species** in the Andaman & Nicobar Islands. - It typically breeds in **shaded pools** in forested areas. *Anopheles stephensi* - **Anopheles stephensi** is a major **urban and rural** malaria vector in mainland India and the Middle East. - It is adapted to **urban environments** and breeds in artificial containers. - It is **not found** in the Andaman & Nicobar Islands. *Anopheles culicifacies* - **Anopheles culicifacies** is the most widespread rural malaria vector in the **Indian subcontinent**. - It breeds in **rice fields**, irrigation channels, and other shallow freshwater bodies. - It is **not present** in the Andaman & Nicobar Islands due to the distinct island ecology.

Q: Index for estimating epidemic of plague?

Cheopis index. ***Cheopis index*** - This index is specifically used to assess the potential for a **plague outbreak** by measuring the average number of **Xenopsylla cheopis (oriental rat flea)** per rat. - A value of **1 or more** indicates a high risk of plague transmission. *Burrow index* - The burrow index is used to estimate rodent population density by counting **active burrows**. - While relevant to rodent control, it does not directly measure the **flea burden specific to plague transmission**. *Total flea index* - The total flea index is the average number of **all flea species** per rodent. - While it gives a general idea of flea infestation, it's not as specific as the Cheopis index for **plague transmission risk**, which primarily involves **X. cheopis**. *None of the options* - The **Cheopis index** is a well-established and widely used epidemiological tool for assessing plague risk. - Therefore, there is a correct option among the choices provided.

Q: A 2-year-old child diagnosed provisionally with diphtheria and on examination she has greyish white membrane patch around her tonsils. The child has a 6-year-old sibling at home, who is fully immunized as per the schedule. What is the best measure to prevent disease in the sibling of the child?

Prophylactic erythromycin to be given. ***Prophylactic erythromycin to be given*** - All **close contacts** of a diphtheria patient, regardless of their immunization status, should receive **antibiotic prophylaxis** to eliminate carriage of *C. diphtheriae*. - **Erythromycin** is a commonly recommended antibiotic for this purpose, given its effectiveness against the bacteria. *Nothing is required to be done* - This is incorrect because, even if immunized, a close contact can still be a **carrier** of *C. diphtheriae* and transmit the infection to others. - **Diphtheria toxin** can still be produced by carriers, posing a risk of disease development if not cleared. *Full course of DPT* - This is unnecessary for a fully immunized child; a full course is typically for **unimmunized** or **incompletely immunized** - **Antibiotic prophylaxis** is the immediate priority for preventing illness in contacts. *Booster dose of DPT* - A booster dose offers **active immunity** but does not immediately address potential asymptomatic carriage of *C. diphtheriae*. - The primary goal for a contact is to eliminate the bacteria, which antibiotics can achieve more rapidly.

Question 1

What is the recommended period of isolation for a suspected case of diphtheria?

Accepted Answer

14 days

Answer

12 days

Answer

10 days

Answer

7 days

Question 2

To prevent KFD which of the following is not used?

Accepted Answer

Deforestation

Answer

Self protection against ticks

Answer

Control of cattle roaming in the forest

Answer

Vaccination

Question 3

True about epidemiology of cholera-

Accepted Answer

Food can transmit the disease

Answer

Boiling water cannot destroy the organism

Answer

Vaccination gives 90% protection

Answer

Cholera cannot be transmitted by contaminated water

Question 4

All are zoonotic disease except -

Accepted Answer

Scabies

Answer

Leptospirosis

Answer

Rabies

Answer

Brucellosis

Question 5

Maximum consumption of antibiotics occurs for:

Accepted Answer

Animal non-therapeutic use

Answer

Human non-therapeutic use

Answer

Human therapeutic use

Answer

Animal therapeutic use

Question 6

Mycobacterium tuberculosis infection in human is most commonly because of -

Accepted Answer

Inhalation

Answer

Ingestion

Answer

Inoculation

Answer

Contact

Question 7

A boy got an unprovoked bite from a neighbour's dog. The animal control authority caught the dog and it was found to be healthy. What is the most appropriate next step in the management of the dog?

Accepted Answer

Observe the dog for 10 days for signs of rabies

Answer

Test antibody level in the dog

Answer

Perform euthanasia for the dog

Answer

Start post-exposure prophylaxis

Question 8

Species of Anopheles causing malaria in Andaman & Nicobar island?

Accepted Answer

Anopheles epiroticus

Answer

Anopheles dirus

Answer

Anopheles stephensi

Answer

Anopheles culicifacies

Question 9

Index for estimating epidemic of plague?

Accepted Answer

Cheopis index

Answer

Burrow index

Answer

Total flea index

Answer

None of the options

Question 10

A 2-year-old child diagnosed provisionally with diphtheria and on examination she has greyish white membrane patch around her tonsils. The child has a 6-year-old sibling at home, who is fully immunized as per the schedule. What is the best measure to prevent disease in the sibling of the child?

Accepted Answer

Prophylactic erythromycin to be given

Answer

Nothing is required to be done

Answer

Full course of DPT

Answer

Booster dose of DPT

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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