Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 621: Which of the following infectious diseases has the highest proportion of asymptomatic chronic carriers?

A. Measles
B. Rabies
C. Diphtheria
D. Hepatitis B (Correct Answer)

Explanation: ***Hepatitis B*** - **Hepatitis B** infection has a significant proportion of **chronic asymptomatic carriers**, particularly when infection occurs perinatally or in early childhood. - In adults, approximately **5% develop chronic infection** after acute exposure, and many of these chronic carriers remain asymptomatic while maintaining infectivity. - Chronic carriers can harbor the virus for years or decades without clinical symptoms, making them an important reservoir for transmission. - This is a major public health concern as asymptomatic carriers can unknowingly transmit the virus. *Measles* - **Measles** is highly contagious and typically presents with **symptomatic disease** in nearly all infected individuals. - Clinical features include characteristic maculopapular rash, cough, coryza, conjunctivitis, and Koplik's spots. - Asymptomatic infection is **extremely rare** with measles virus. *Diphtheria* - While **asymptomatic pharyngeal carriage** of *Corynebacterium diphtheriae* can occur, it is not the predominant pattern. - Clinical diphtheria typically presents with pseudomembrane formation, sore throat, and potential systemic toxin effects. - Carrier rates vary but are not as epidemiologically significant as with Hepatitis B. *Rabies* - **Rabies** is almost **100% symptomatic** once the virus reaches the central nervous system. - There is **no chronic asymptomatic carrier state** in humans. - Once clinical symptoms appear (encephalitis, hydrophobia, paralysis), the disease is virtually always fatal.

Question 622: Under NTEP, what is the honorarium given to a DOTS provider after the completion of treatment?

A. 150 INR
B. 500 INR (Correct Answer)
C. 1000 INR
D. 250 INR

Explanation: ***500 INR*** - Under the **National Tuberculosis Elimination Programme (NTEP)**, a **DOTS provider** receives an honorarium of **INR 500** upon the successful completion of tuberculosis treatment for a **new TB patient**. - This incentive, revised from the earlier amount of INR 250, aims to recognize the crucial role of DOTS providers in ensuring treatment adherence and successful outcomes. - The increased honorarium reflects the government's commitment to incentivizing community participation in TB elimination. *150 INR* - This amount is **significantly lower than the stipulated honorarium** for a DOTS provider upon treatment completion under current NTEP guidelines. - The correct incentive for successful completion of treatment is INR 500 for new TB cases. *250 INR* - This was the **earlier honorarium amount** under the previous NTEP guidelines, which has since been **revised upward**. - Under the current NTEP incentive structure, the honorarium for treatment completion has been increased to INR 500. *1000 INR* - This amount is **higher than the designated honorarium** for a DOTS provider upon treatment completion under NTEP. - While this figure may apply to other incentive schemes or different milestones, the standard honorarium for new TB case completion is INR 500.

Question 623: In the context of malaria control, when is regular insecticidal spray recommended based on the Annual Parasite Index (API)?

A. < 1
B. < 2
C. > 2 (Correct Answer)
D. > 1

Explanation: ***> 2*** - Regular insecticidal spray, particularly **Indoor Residual Spraying (IRS)**, is a key malaria control measure recommended when the **Annual Parasite Index (API) is greater than 2**. - An API greater than 2 indicates **high endemicity** with a significant burden of malaria transmission in the community, necessitating aggressive vector control strategies. - According to **NVBDCP (National Vector Borne Disease Control Programme) guidelines**, API > 2 defines high-risk areas where routine IRS is implemented as a core intervention. *> 1* - An API between 1-2 represents **moderate endemicity**, where the focus is primarily on **active case detection, prompt treatment, and targeted interventions** rather than universal spraying. - While vector control remains important, routine widespread IRS is not the standard recommendation at this threshold. *< 2* - An API of less than 2 (which includes both moderate and low endemic areas) does not routinely warrant universal insecticidal spraying programs. - In areas with API < 2, **case management, surveillance, and selective vector control** are prioritized over widespread IRS campaigns. *< 1* - An API of less than 1 indicates **low endemicity**, where malaria transmission is minimal and sporadic. - In such areas, **surveillance, prompt case detection and treatment, and targeted interventions** are the mainstay, with IRS reserved only for focal outbreaks or high-risk pockets.

Question 624: Pneumonic plague is spread by:

A. Direct contact with infected tissue
B. Bite of infected flea
C. Ingestion of contaminated food
D. Droplet infection (Correct Answer)

Explanation: ***Correct: Droplet infection*** - Pneumonic plague is a severe form of plague that affects the **lungs** and is transmitted through **respiratory droplets** expelled by an infected person or animal during coughing or sneezing. - This direct person-to-person transmission distinguishes it from other forms of plague. - It is the **only form of plague** that can spread directly from human to human without an animal or flea vector. *Incorrect: Bite of infected flea* - This is the primary mode of transmission for **bubonic plague**, where the bacterium *Yersinia pestis* is transmitted from rodents to humans via infected fleas. - While bubonic plague can progress to pneumonic plague, the initial transmission route for the pneumonic form itself is not flea bites. *Incorrect: Direct contact with infected tissue* - Direct contact with infected tissues or fluids can lead to **septicemic plague** or sometimes bubonic plague, especially in cases where there is a break in the skin. - This is not the typical or primary route for the spread of pneumonic plague, which is respiratory. *Incorrect: Ingestion of contaminated food* - Ingestion of contaminated food or water is a route for various **gastrointestinal infections** and diseases like salmonella or cholera. - It is not a known or common method for the transmission of any form of plague, including pneumonic plague.

Question 625: Which of the following statements about pathogenic mosquitoes is correct?

A. Mansonia mosquitoes lay their eggs in rafts.
B. Culex mosquitoes are primarily vectors for West Nile virus.
C. Aedes mosquitoes are known for their distinctive black and white striped markings.
D. Anopheles mosquitoes are known for transmitting malaria. (Correct Answer)

Explanation: ***Correct: Anopheles mosquitoes are known for transmitting malaria.*** - **Anopheles mosquitoes** are the **primary and only vectors** for **malaria**, a parasitic disease caused by Plasmodium parasites. - They transmit the parasite through their **saliva** when they bite humans, typically during **dusk and dawn**. - This is the most significant pathogenic association among the options. *Incorrect: Mansonia mosquitoes lay their eggs in rafts.* - **Mansonia mosquitoes** lay their eggs in **clusters attached to underwater parts of aquatic plants**, not in rafts. - **Culex mosquitoes** are the ones that lay their eggs in **raft-like formations** on water surfaces. *Incorrect: Culex mosquitoes are primarily vectors for West Nile virus.* - While **Culex mosquitoes** can transmit West Nile virus, in the **Indian context** they are primarily known as vectors for **lymphatic filariasis** (Wuchereria bancrofti) and **Japanese encephalitis**. - West Nile virus is more relevant in Western countries and is not the primary disease association for Culex in India. *Incorrect: Aedes mosquitoes are known for their distinctive black and white striped markings.* - While **Aedes aegypti** and **Aedes albopictus** do have **black and white striped markings**, this is a **morphological characteristic** rather than a primary **pathogenic association**. - The question asks about pathogenic mosquitoes, and Aedes is better characterized by its **disease transmission** (dengue, Zika, chikungunya, yellow fever) rather than its appearance. - As a pathogenic mosquito, its **daytime biting behavior** and **urban breeding habits** are more relevant than its markings.

Question 626: Which of the following statements about influenza infectivity is correct?

A. Communicable period is 1 day before to 5-7 days after the onset of symptoms
B. All of the options are correct. (Correct Answer)
C. There can be subclinical cases of influenza.
D. The primary source of infection is a clinical case.

Explanation: ***All of the options are correct.*** - All statements provided accurately describe aspects of influenza infectivity and epidemiology. - The **communicable period**, the **primary source of infection**, and the potential for **subclinical cases** are all characteristic features of influenza. *Communicable period is 1 day before to 5-7 days after the onset of symptoms* - This statement is accurate, as influenza is transmissible **before symptom onset** and for several days afterward, which contributes to its rapid spread. - Peak viral shedding often occurs just before and in the first few days of symptomatic illness. - Adults typically shed virus from 1 day before to 5-7 days after symptom onset (can be longer in children and immunocompromised individuals). *The primary source of infection is a clinical case.* - This is correct, as **symptomatic individuals (clinical cases) are the PRIMARY source** of influenza virus transmission to others. - Respiratory droplets produced by coughing, sneezing, or talking from an infected person are the main mode of spread. - While subclinical cases can transmit, clinical cases with overt symptoms produce more respiratory droplets and are the major drivers of transmission. *There can be subclinical cases of influenza.* - This statement is correct; many individuals infected with influenza virus experience **mild or asymptomatic infections** (subclinical cases). - These subclinical cases can still transmit the virus, though typically to a lesser extent than symptomatic cases, further complicating control efforts.

Question 627: Behavioral surveillance survey is done in?

A. AIDS (Correct Answer)
B. TB
C. Filaria
D. Malaria

Explanation: ***AIDS*** - Behavioral surveillance surveys are crucial for understanding and monitoring behaviors related to **HIV transmission**, such as sexual practices and drug use, among at-risk populations. - These surveys help in designing and evaluating **prevention programs** by identifying trends in risky behaviors and knowledge, attitudes, and practices (KAP) concerning HIV. *Filaria* - Surveillance for filaria primarily involves **entomological surveys** (mosquito monitoring) and **parasitological surveys** (blood examinations for microfilariae). - Behavioral aspects are less central to direct surveillance compared to disease vectors and infection rates. *TB* - Tuberculosis surveillance mainly focuses on **case detection**, **treatment outcomes**, and monitoring **drug resistance** through clinical and laboratory data. - While patient adherence to treatment involves behavior, there isn't a dedicated "behavioral surveillance survey" method specifically for TB. *Malaria* - Malaria surveillance involves monitoring **parasitemia rates**, **vector populations**, and **antimalarial drug resistance**. - Behavioral components like bed net usage are important, but the primary surveillance methods are not termed "behavioral surveillance surveys" in the same structured way as for HIV.

Question 628: Droplet nuclei is a type of ?

A. Direct transmission of infectious agents
B. Vertical transmission of pathogens
C. Biological transmission of pathogens
D. Indirect transmission of pathogens (Correct Answer)

Explanation: ***Indirect transmission of pathogens*** - **Droplet nuclei** are tiny airborne particles remaining after the evaporation of respiratory droplets, suspended in the air for prolonged periods, allowing pathogens to travel over longer distances. - This mode of transmission is considered **indirect** because it involves an environmental medium (air) rather than direct contact between individuals. *Vertical transmission of pathogens* - This refers to the transmission of a pathogen from a **mother to her offspring**, either during pregnancy, childbirth, or breastfeeding. - Examples include HIV and rubella, which are transmitted directly from parent to child, unlike airborne droplet nuclei. *Direct transmission of infectious agents* - This involves immediate physical contact or exposure between an infected individual and a susceptible host (e.g., touching, kissing, sexual contact). - It does not involve an intermediate environmental vehicle such as airborne particles that travel through the air from their source. *Biological transmission of pathogens* - This type of transmission involves an **arthropod vector** that not only transmits the pathogen but also allows it to multiply or develop within its body before transmission. - Examples include malaria transmitted by mosquitoes or Lyme disease by ticks, which is distinct from airborne droplet nuclei transmission.

Question 629: What is the definition of a reservoir in the context of infectious diseases?

A. Person, animal or object from which infectious agent is transmitted to host
B. Person, animal or substance in which infectious agent lives and multiplies (Correct Answer)
C. Person or animal in which infectious agent causes a disease
D. Person or animal that transmits the infectious agent mechanically

Explanation: ***Person, animal or substance in which infectious agent lives and multiplies*** - A **reservoir** is the natural habitat where an **infectious agent** normally lives and multiplies, and from which it can be transmitted to a susceptible host. - This definition emphasizes residence and replication, not necessarily direct transmission to a new host or causation of disease in the reservoir itself. - Examples include humans (e.g., typhoid carriers), animals (e.g., rodents for plague), and environmental sources (e.g., soil for tetanus). *Person, animal or object from which infectious agent is transmitted to host* - This option describes a **source of infection**, which can be a reservoir but isn't always. A source is where a host acquires the infection, but not necessarily where the pathogen multiplies. - An object (fomite) can be a source of infection, but it's rarely a reservoir because pathogens generally do not live and multiply there for extended periods. *Person or animal in which infectious agent causes a disease* - This describes a **diseased host** or a **case**, not necessarily a reservoir. A reservoir may or may not experience disease from the pathogen it harbors. - For example, a **carrier** can be a reservoir without showing symptoms of disease. *Person or animal that transmits the infectious agent mechanically* - This describes a **vector**, particularly a mechanical vector (e.g., flies carrying pathogens on their body). - Unlike a reservoir, a vector does not provide a habitat where the pathogen lives and multiplies; it merely transports it from one location to another.

Question 630: Which of the following is the most epidemiologically distinctive feature of chickenpox?

A. Caused by varicella-zoster virus
B. Most commonly affects children under 10 years old
C. Secondary attack rate (SAR) is approximately 90% (Correct Answer)
D. Infectious period is 1-2 days before rash until all blisters have scabbed over

Explanation: ***Secondary attack rate (SAR) is approximately 90%*** - A **secondary attack rate (SAR)** of around 90% is exceptionally high, indicating that chickenpox is one of the most **contagious infectious diseases**, readily spreading among susceptible household contacts. - This high SAR highlights the disease's **distinctive epidemiological characteristic** of efficient person-to-person transmission within close-contact settings. *Caused by varicella-zoster virus* - While true, many diseases are caused by specific viruses, and this fact alone is not an **epidemiologically distinctive feature** in terms of transmissibility or population impact. - The causative agent defines the disease, but doesn't uniquely describe its spread or contagiousness in an epidemiological sense. *Most commonly affects children under 10 years old* - Many common childhood infections, such as measles or mumps, also primarily affect children, making this less of a **distinctive epidemiological feature** for chickenpox specifically. - The age group affected is common for many highly transmissible diseases of childhood. *Infectious period is 1-2 days before rash until all blisters have scabbed over* - Many infectious diseases have similar **infectious periods** spanning from a prodromal phase to resolution, making this a general feature of viral infections rather than one highly distinctive to chickenpox epidemiologically. - While important for infection control, it doesn't stand out as uniquely characteristic of chickenpox's epidemiological profile compared to other common infectious diseases.

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Communicable Disease Control Principles

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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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