Infectious Diseases Practice Questions

Q: Spread of chickenpox is maximum when?

Just before and after onset of rash. ***Just before and after onset of rash*** - The period of maximum infectivity for chickenpox (varicella) is typically 1-2 days **before the onset of the rash** and continues for 4-5 days after the rash appears, or until all lesions have crusted over. - During this time, the **varicella-zoster virus** is actively replicating and shedding from the respiratory tract and skin lesions, making it highly transmissible. *After formation of scab* - Once all lesions have dried and **formed scabs**, the individual is generally no longer considered contagious. - The virus is no longer actively shed from crusted lesions, significantly reducing the risk of transmission. *One week before onset of rash* - While there might be some viral shedding during the **incubation period**, significant contagiousness usually begins closer to the rash onset (1-2 days prior). - A full week before the rash, viral replication might be occurring, but the quantity of shed virus is typically too low to cause widespread transmission. *During convalescence* - **Convalescence** refers to the period of recovery after the acute illness, which begins once all lesions have scabbed over. - During this stage, the individual is usually no longer infectious, as the active viral shedding has ceased.

Q: Case finding in the Revised National Tuberculosis Control Programme (RNTCP), now known as the National Tuberculosis Elimination Programme (NTEP), is based on which of the following diagnostic methods?

Sputum microscopy. ***Sputum microscopy*** - The **National Tuberculosis Elimination Programme (NTEP)**, formerly known as the **Revised National Tuberculosis Control Programme (RNTCP)**, primarily relies on **sputum smear microscopy** for case finding of pulmonary TB due to its cost-effectiveness, speed, and widespread availability in resource-limited settings. - It identifies individuals who are **smear-positive**, meaning they are actively shedding bacteria and are highly infectious. - Sputum microscopy remains the **cornerstone of case finding** in the program despite the availability of newer diagnostic methods. *Mantoux test* - The **Mantoux test** (Tuberculin Skin Test) is used to detect **TB infection**, not active TB disease, and does not differentiate between latent infection and active disease. - It is not used for primary case finding in NTEP due to its limitations in specificity and sensitivity, especially in BCG-vaccinated populations. *Chest X-ray* - **Chest X-ray** is a valuable diagnostic tool for active TB, but it is typically used as a **supplementary investigation** or for screening specific populations, not as the primary diagnostic method for routine case finding in NTEP. - Its use requires specialized equipment and trained personnel, making it less feasible for widespread primary screening compared to sputum microscopy. *Sputum culture* - **Sputum culture** is the **gold standard** for TB diagnosis and drug susceptibility testing, offering higher sensitivity than microscopy. - However, it is more expensive, takes several weeks to yield results, and requires specialized laboratory facilities, making it impractical as the primary method for routine case finding and initial diagnosis in the NTEP.

Q: What is the diagnostic criterion for sputum-positive tuberculosis (TB)?

At least 1 sputum sample positive for AFB. The definition of sputum-positive TB, particularly in initial diagnosis, generally requires at least one **acid-fast bacilli (AFB) smear-positive** sputum sample [1]. This criterion is crucial for guiding initial treatment strategies and public health interventions for **infectious TB** [1]. While a BACTEC-positive result confirms the presence of **Mycobacterium tuberculosis**, a rapid AFB smear positive result is often the initial criterion for "sputum-positive" classification for immediate management [2]. While some guidelines or clinical contexts might emphasize multiple positive samples for confirmation, the widely accepted minimum for sputum-positive TB is **at least one positive AFB smear** [1].

Q: Leprosy is considered a public health problem if the prevalence of leprosy is more than:

1 per 10,000. ***1 per 10,000*** - The World Health Organization (WHO) defines leprosy as a public health problem if its prevalence is one or more cases per **10,000 population**. - This threshold guides global and national strategies for **leprosy elimination** and control efforts. *2 per 10,000* - While this is a concerning prevalence rate, the internationally accepted threshold for defining leprosy as a public health problem is lower, at **1 per 10,000**. - A rate of 2 per 10,000 would already indicate a significant public health burden, meeting and exceeding the WHO criterion. *5 per 10,000* - This prevalence rate is significantly higher than the WHO's established threshold, indicating an advanced stage of leprosy as a public health problem. - Countries reaching this level of prevalence would require **intensive control measures** and urgent intervention. *10 per 10,000* - A prevalence of 10 per 10,000 signifies a very severe public health crisis regarding leprosy, far exceeding the definition of a public health problem. - At this rate, the disease would be **highly endemic**, requiring immediate and comprehensive public health responses.

Q: Which of the following statements about chickenpox is false?

Crusts contain live varicella-zoster virus.. ***Crusts contain live varicella-zoster virus.*** - The **crusts** or scabs formed during chickenpox typically contain **inactive** or non-infectious viral particles. - The most infectious stages are the **macular, papular, and vesicular** lesions, before they crust over. *Rashes are pleomorphic.* - Chickenpox rash is **pleomorphic**, meaning various stages of lesions (macules, papules, vesicles, and crusts) can be seen simultaneously in the same body area. - This feature, often described as a **"dewdrop on a rose petal"** appearance, is characteristic of varicella. *Rashes are centripetal in distribution.* - The rash of chickenpox typically has a **centripetal distribution**, meaning it is more concentrated on the **trunk** and less so on the extremities. - This pattern helps differentiate it from other vesicular rashes. *Rapid progression from macule to vesicle is observed.* - Chickenpox lesions evolve quickly from a **macule** (flat red spot) to a **papule** (raised bump) and then into a characteristic **vesicle** (fluid-filled blister) within a few hours. - This rapid progression is a hallmark of the disease.

Q: Which of the following represents the WHO recommended message/theme for HIV testing?

Everyone counts. ***Everyone counts*** - "Everyone counts" is the current **WHO recommended message for HIV testing**, emphasizing that reaching all individuals with HIV testing services is crucial to ending the HIV epidemic. - This theme highlights the importance of **equity and access** to testing for all populations, including marginalized and hard-to-reach groups. *Unite for Everyone* - This phrase is not the official slogan or recommendation for **HIV testing** from the WHO. - While promoting unity is important in public health, it does not specifically encapsulate the current **WHO strategy** for HIV testing. *HIV Awareness for All* - This is a general statement about **public health education** but does not represent the specific **WHO recommendation** for HIV testing strategy. - While **awareness** is a component of public health, the current WHO recommendation focuses on a more direct call to action regarding testing. *Health for Everyone* - This is a broad public health message and not the specific **WHO recommendation for HIV testing**. - It represents a general goal of global health efforts rather than a targeted message for **HIV testing initiatives**.

Q: Chemoprophylaxis is not indicated in which of the following?

Measles. ***Measles*** - **Chemoprophylaxis is not routinely indicated for measles** as it is a viral disease primarily prevented by vaccination. - Post-exposure prophylaxis for measles typically involves **measles vaccine** or **immunoglobulin** for susceptible contacts, not antibiotics or antivirals. *Cholera* - **Chemoprophylaxis with antibiotics** (e.g., doxycycline, azithromycin) can be indicated for close contacts of confirmed cholera cases, especially in outbreaks or high-risk settings, to prevent further spread. - This is due to cholera being a bacterial infection that can rapidly transmit through contaminated water and food. *Meningococcemia* - **Chemoprophylaxis is strongly recommended** for close contacts of individuals with invasive meningococcal disease (meningococcemia or meningococcal meningitis) to prevent secondary cases. - Oral **rifampin, ciprofloxacin, or ceftriaxone** are commonly used for this purpose to eliminate carriage of *Neisseria meningitidis*. *Plague* - **Chemoprophylaxis with antibiotics** (e.g., doxycycline, ciprofloxacin) is indicated for individuals with high-risk exposure to plague, such as close contact with an infected person or animal, or laboratory exposure. - This is a serious bacterial infection caused by *Yersinia pestis* where early intervention can prevent severe disease and death.

Q: Among the following diseases where chemoprophylaxis is considered for epidemiological control, it is least practical for:

Tuberculosis. ***Tuberculosis*** - **Chemoprophylaxis exists** for TB (isoniazid, rifampin regimens) but is the **least practical** for population-level epidemiological control due to **prolonged treatment duration** (6-9 months). - Results in **poor adherence**, high dropout rates, and significant risk of **drug resistance** when implemented as mass chemoprophylaxis, making it impractical for large-scale control. *Measles* - Has **no antimicrobial chemoprophylaxis** available - measles is a **viral infection** with no effective prophylactic antibiotics. - Post-exposure **immune globulin** is passive immunization, not chemoprophylaxis, making this option **not applicable** rather than "least practical." *Cholera* - **WHO does not recommend** antibiotic chemoprophylaxis for cholera control due to **ineffectiveness** and **antibiotic resistance** concerns. - Since chemoprophylaxis is **contraindicated** rather than impractical, this option is **not applicable** to the question of practicality. *Diphtheria* - **Chemoprophylaxis is highly practical** with **erythromycin or penicillin** for close contacts over **short duration** (7-10 days). - Demonstrates **good compliance** and effectiveness in **outbreak control**, making it the most practical chemoprophylaxis option among those that actually use it.

Q: In which of the following conditions is mass prophylaxis typically recommended during outbreaks?

Scabies outbreak. ***Scabies outbreak*** - **Mass treatment** of all exposed individuals is the standard outbreak response for scabies, especially in institutional settings like nursing homes, schools, hostels, or military barracks. - This involves **simultaneous treatment** of both symptomatic cases and asymptomatic contacts to break the transmission cycle during an active outbreak. - This is the only option that requires an immediate, coordinated mass intervention specifically in response to an outbreak situation. *Vitamin A deficiency outbreak* - Vitamin A supplementation is a **nutritional intervention** for endemic deficiency, not an infectious disease requiring mass prophylaxis. - While important for child health programs, it does not address pathogen transmission or outbreak control. *Worm infestation outbreak* - Mass deworming programs exist but are typically **routine, periodic interventions** in endemic areas rather than emergency outbreak responses. - These are scheduled control programs (e.g., biannual school-based deworming) not triggered by acute outbreaks. - They are part of long-term helminth control strategies, not rapid outbreak management. *Lymphatic filariasis outbreak* - **Mass drug administration (MDA)** for filariasis is a multi-year **elimination strategy** in endemic regions, not an outbreak response. - Lymphatic filariasis does not present as acute outbreaks requiring immediate mass prophylaxis. - MDA campaigns are planned, systematic interventions targeting entire endemic populations over 5-6 years.

Question 1

Spread of chickenpox is maximum when?

Accepted Answer

Just before and after onset of rash

Answer

After formation of scab

Answer

One week before onset of rash

Answer

During convalescence

Question 2

Case finding in the Revised National Tuberculosis Control Programme (RNTCP), now known as the National Tuberculosis Elimination Programme (NTEP), is based on which of the following diagnostic methods?

Accepted Answer

Sputum microscopy

Answer

Mantoux test

Answer

Chest X-ray

Answer

Sputum culture

Question 3

What is the diagnostic criterion for sputum-positive tuberculosis (TB)?

Accepted Answer

At least 1 sputum sample positive for AFB

Answer

BACTEC positive

Answer

No positive samples

Answer

2 out of 3 sputum samples positive

Question 4

Leprosy is considered a public health problem if the prevalence of leprosy is more than:

Accepted Answer

1 per 10,000

Answer

2 per 10,000

Answer

5 per 10,000

Answer

10 per 10,000

Question 5

Which of the following statements about chickenpox is false?

Accepted Answer

Crusts contain live varicella-zoster virus.

Answer

Rashes are centripetal in distribution.

Answer

Rashes are pleomorphic.

Answer

Rapid progression from macule to vesicle is observed.

Question 6

Which of the following represents the WHO recommended message/theme for HIV testing?

Accepted Answer

Everyone counts

Answer

Unite for Everyone

Answer

HIV Awareness for All

Answer

Health for Everyone

Question 7

Chemoprophylaxis is not indicated in which of the following?

Accepted Answer

Measles

Answer

Meningococcemia

Answer

Cholera

Answer

Plague

Question 8

Which of the following statements is true regarding the epidemiology of influenza?

Accepted Answer

Asymptomatic cases can occur and may contribute to transmission.

Answer

Pandemics cannot occur with influenza viruses.

Answer

Incubation period is typically 7-10 days.

Answer

Humans are the only reservoir for influenza.

Question 9

Among the following diseases where chemoprophylaxis is considered for epidemiological control, it is least practical for:

Accepted Answer

Tuberculosis

Answer

Measles

Answer

Cholera

Answer

Diphtheria

Question 10

In which of the following conditions is mass prophylaxis typically recommended during outbreaks?

Accepted Answer

Scabies outbreak

Answer

Vitamin A deficiency outbreak

Answer

Worm infestation outbreak

Answer

Lymphatic filariasis outbreak

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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