Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 471: What is the recommended period of isolation for a suspected case of diphtheria?

A. 12 days
B. 10 days
C. 14 days (Correct Answer)
D. 7 days

Explanation: ***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.

Question 472: To prevent KFD which of the following is not used?

A. Self protection against ticks
B. Control of cattle roaming in the forest
C. Vaccination
D. Deforestation (Correct Answer)

Explanation: ***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**.

Question 473: All are zoonotic disease except -

A. Leptospirosis
B. Rabies
C. Scabies (Correct Answer)
D. Brucellosis

Explanation: ***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.

Question 474: Maximum consumption of antibiotics occurs for:

A. Human non-therapeutic use
B. Human therapeutic use
C. Animal non-therapeutic use (Correct Answer)
D. Animal therapeutic use

Explanation: ***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.

Question 475: Mycobacterium tuberculosis infection in human is most commonly because of -

A. Ingestion
B. Inhalation (Correct Answer)
C. Inoculation
D. Contact

Explanation: ***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.

Question 476: 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?

A. Test antibody level in the dog
B. Perform euthanasia for the dog
C. Start post-exposure prophylaxis
D. Observe the dog for 10 days for signs of rabies (Correct Answer)

Explanation: ***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.

Question 477: Which of the following diseases has an incubation period > 10 days

A. Plague
B. Cholera
C. Influenza
D. Measles (Correct Answer)

Explanation: ***Correct: Measles*** - Measles has a relatively long incubation period, typically ranging from **10 to 14 days** from exposure to the onset of fever. - This extended incubation allows for significant asymptomatic spread before the classic **maculopapular rash** appears. - Among the listed options, only measles exceeds the 10-day threshold. *Incorrect: Plague* - The incubation period for **bubonic plague** is usually 2 to 6 days. - For **pneumonic plague**, the incubation period is even shorter, typically 1 to 3 days. - Both forms are well below 10 days. *Incorrect: Cholera* - Cholera has a very short incubation period, ranging from a few hours to 5 days, usually **2-3 days**. - This rapid onset is due to the toxin production in the small intestine causing severe **watery diarrhea**. *Incorrect: Influenza* - The incubation period for influenza is generally short, averaging around 2 days, and can range from **1 to 4 days**. - This short incubation period contributes to its rapid spread during outbreaks.

Question 478: True statement about plague is -

A. Septicemic plague is highly infectious
B. Live attenuated vaccines are used
C. Vaccine is not used to control epidemic of pneumonic plague
D. Most important measure to control epidemic is rodent control (Correct Answer)

Explanation: ***Most important measure to control epidemic is rodent control*** - **Plague** is a zoonotic disease primarily affecting rodents, with human infection occurring through flea bites from infected rodents. **Rodent control** is the fundamental and most important measure for plague control as it breaks the transmission cycle at its source. - While immediate epidemic response includes case isolation, antibiotic treatment, and contact prophylaxis, **rodent control remains the cornerstone of comprehensive plague control programs** and is essential for both preventing and controlling epidemics. - The bacterium *Yersinia pestis* is maintained in nature within **rodent populations**, making their management the primary long-term public health intervention. *Septicemic plague is highly infectious* - **Septicemic plague** is a severe form where bacteria multiply in the bloodstream but is **not infectious** from person to person - there is no person-to-person transmission. - **Pneumonic plague** (lung infection) is the only form that is highly infectious and can spread directly between humans via respiratory droplets. *Live attenuated vaccines are used* - Live attenuated vaccines for plague have been used historically but are **not currently recommended or widely available** for routine use. - Modern plague control relies on antibiotics (streptomycin, gentamicin, doxycycline) rather than vaccination. - Vaccine development continues, but no vaccine is currently licensed for general use in most countries. *Vaccine is not used to control epidemic of pneumonic plague* - While this statement is technically true, it is phrased as a negative statement and doesn't represent the most important or fundamental concept about plague control. - The question asks for the "true statement" and the positive statement about **rodent control being the most important measure** is the best answer as it represents the core principle of plague epidemiology and control.

Question 479: Which of the following actions can help in the prevention of HIV transmission?

A. Avoidance of smoking by drivers
B. Use of copper T by sex workers
C. Using safe injection techniques (Correct Answer)
D. Prohibiting voluntary blood donation

Explanation: ***Using safe injection techniques*** - HIV can be transmitted through the sharing of needles and syringes, particularly among **intravenous drug users**, due to the direct transfer of infected blood. - Practicing **safe injection techniques**, such as using sterile needles and syringes for each injection, significantly reduces the risk of HIV transmission in these populations. *Avoidance of smoking by drivers* - This action is primarily related to **respiratory health** and **traffic safety**, as smoking can lead to lung diseases and impair concentration. - It has **no direct relevance** to the prevention of human immunodeficiency virus (HIV) transmission. *Use of copper T by sex workers* - A **copper T (intrauterine device)** is a form of contraception that prevents pregnancy by creating a local inflammatory reaction in the uterus. - It does **not offer protection** against sexually transmitted infections (STIs), including HIV, which requires barrier methods like condoms for prevention. *Prohibiting voluntary blood donation* - **Voluntary blood donation** is a crucial source of blood products for medical treatments and emergencies. Screening practices ensure the safety of donated blood. - Prohibiting it would **deplete blood supplies** and does not prevent HIV transmission, as modern blood screening protocols effectively identify and discard HIV-infected blood units.

Question 480: The incubation period for polio is

A. 1 - 2 years
B. 7 - 14 days (Correct Answer)
C. 2 - 3 weeks
D. 3 - 7 days

Explanation: **7 - 14 days** - The **incubation period** for poliovirus, from exposure to the onset of initial symptoms, typically ranges from **7 to 14 days**. - This period allows the virus to replicate in the **gastrointestinal tract** and lymphatic tissue before potentially invading the central nervous system. *1 - 2 years* - An incubation period of **1-2 years** is far too long for poliovirus and is characteristic of diseases like **Kuru** or certain **slow viral infections**. - Poliovirus progresses much more rapidly, typically within weeks. *2 - 3 weeks* - While some viral infections can have an incubation period of **2-3 weeks**, this is slightly longer than the typical range for poliovirus. - The average presentation for polio symptoms is usually within the second week post-exposure. *3 - 7 days* - An incubation period of **3-7 days** is possible for some very rapidly acting viruses, but it is generally a bit shorter than the common range for poliovirus. - Most poliovirus cases manifest symptoms closer to the one-to-two-week mark.

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Communicable Disease Control Principles

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Vector-Borne Diseases

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Water-Borne Diseases

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Air-Borne Diseases

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Zoonotic Diseases

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Sexually Transmitted Infections

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HIV/AIDS Control Program

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Tuberculosis Control

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Leprosy Elimination

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Emerging and Re-emerging Infections

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Hospital-Acquired Infections

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Integrated Disease Surveillance Project

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