Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 611: Which software is specifically designed for monitoring the tuberculosis control programme under the National Tuberculosis Elimination Programme (NTEP), formerly RNTCP, in India?

A. NICHAY
B. NIKSHAY (Correct Answer)
C. E-DOTS
D. NIRBHAI

Explanation: ***NIKSHAY*** - **NIKSHAY** is the dedicated web-based solution for managing the **National Tuberculosis Elimination Programme (NTEP)** in India. - It is used for comprehensive TB patient management, from registration and treatment monitoring to drug stock management and outcome recording. *NICHAY* - "NICHAY" is a misspelling and does not refer to any official software or program associated with TB control in India. - This option is intended as a plausible-sounding distractor based on the correct answer. *E-DOTS* - **DOTS (Directly Observed Treatment, Short-course)** is a strategy for TB treatment delivery, not a specific software platform in India. - While electronic systems are used for DOTS, "E-DOTS" is a general term and not the official name of the NTEP monitoring software. *NIRBHAI* - "NIRBHAI" is not related to any official software or initiative for tuberculosis control under the NTEP in India. - This is a distractor and does not correspond to any known medical or public health program.

Question 612: Among the following options, the minimum acceptable Rideal-Walker coefficient for disinfectant used for cholera stool would be?

A. 4
B. 10
C. 2 (Correct Answer)
D. 7

Explanation: ***2 (Minimum acceptable among given options)*** - The **Rideal-Walker coefficient** measures disinfectant efficacy relative to phenol as the standard reference - A coefficient of **2** means the disinfectant is **twice as effective** as phenol against test organisms (*Salmonella typhi* and *Staphylococcus aureus*) - While higher coefficients are preferred for highly infectious materials like cholera stool, **2 represents the minimum acceptable threshold** among the given options that still provides reasonable disinfection efficacy - Standard practice recommends disinfectants with RW coefficient ≥5 for cholera stool, but among the choices provided, 2 is the lowest that meets basic acceptability criteria *4 (Better choice but not the minimum)* - A coefficient of **4** means the disinfectant is **four times more effective** than phenol - This provides **more robust disinfection** and would be preferred over a coefficient of 2 - However, the question specifically asks for the **minimum acceptable** value, not the optimal value - Among the options, this is not the minimum *7 (Highly effective)* - A coefficient of **7** indicates the disinfectant is **seven times more potent** than phenol - This represents **very good disinfection efficacy** and exceeds minimum requirements - This is well above the minimum acceptable threshold *10 (Excellent efficacy)* - A coefficient of **10** means the disinfectant is **ten times more effective** than phenol - This represents **excellent disinfection power** with a very high safety margin - While ideal for high-risk situations, this far exceeds the minimum acceptable requirement

Question 613: 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 614: 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 615: Which of the following is an example of indirect transmission by a living vector?

A. Transmission by mosquito (Correct Answer)
B. Vertical transmission
C. Soil contact
D. Droplet infection

Explanation: ***Transmission by mosquito*** - This is the classic example of **vector-borne transmission**, where a living biological vector (the mosquito) acts as an intermediary to transmit the infectious agent from an infected host to a susceptible one. - The disease-causing microorganism does not pass directly from person to person but is carried and transmitted by the living vector. - Examples include malaria, dengue, and filariasis. *Vertical transmission* - This refers to transmission of disease from a **mother to her child** during pregnancy, childbirth, or breastfeeding. - This is a form of **direct transmission** where the pathogen passes directly between biologically related individuals without an intermediate living vector. *Soil contact* - This represents **vehicle-borne transmission** where soil acts as a non-living vehicle (fomite) carrying pathogens. - While this is technically indirect transmission, it does not involve a **living biological vector** as specified in the question. - Examples include tetanus, hookworm, and ascariasis transmitted through contaminated soil. *Droplet infection* - This is a form of **direct transmission** where infectious droplets are expelled from the respiratory tract of an infected person and directly contact the mucous membranes of a susceptible person. - The droplets travel a short distance in close proximity, representing direct person-to-person transfer without any intermediate vector.

Question 616: Which of the following is not a recognized transmission route for amoebiasis?

A. Sexual transmission
B. Blood and blood products
C. Vector transmission (Correct Answer)
D. Fecal-oral route

Explanation: ***Vector transmission*** - Amoebiasis, caused by *Entamoeba histolytica*, is primarily an **intestinal infection** transmitted through the **fecal-oral route**. - Its life cycle **does not involve any arthropod vector** (e.g., mosquito, tick, fly) for transmission. - This is the **only route among the options that is definitively NOT recognized** for amoebiasis transmission. *Sexual transmission* - Amoebiasis **can be transmitted** through **oral-anal sexual contact**, particularly documented in men who have sex with men (MSM). - This represents an **indirect fecal-oral transmission** route and is a recognized mode of spread. *Blood and blood products* - While *E. histolytica* can disseminate to cause **amoebic liver abscesses** and rarely systemic disease, transmission via blood transfusion is **extremely rare and not well-documented**. - However, theoretically possible in cases of parasitemia during invasive disease. - Unlike vector transmission, this cannot be definitively ruled out as "not recognized." *Fecal-oral route* - This is the **primary and most important transmission route** for amoebiasis. - Infection occurs through ingestion of **cysts** from contaminated food, water, or through direct person-to-person contact with poor hand hygiene.

Question 617: 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 618: 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 619: 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 620: What is the most common mode of transmission of HIV?

A. Occupational exposure (needle stick injury)
B. Perinatal transmission (mother to child)
C. Sexual contact (Correct Answer)
D. Transmission via blood and blood products

Explanation: ***Sexual contact*** - **Unprotected sexual intercourse**, both heterosexual and homosexual, is overwhelmingly the most common way HIV is transmitted globally. - The virus can be exchanged through **bodily fluids** such as semen, vaginal fluids, and rectal fluids during sexual activity. - Accounts for approximately **80% of new HIV infections** worldwide. *Occupational exposure (needle stick injury)* - While a recognised mode of transmission, **needle stick injuries** account for a very small percentage of total HIV infections, primarily affecting healthcare workers. - The risk of transmission per exposure is relatively low (approximately **0.3%**), especially compared to sexual contact. *Perinatal transmission (mother to child)* - **Mother-to-child transmission** can occur during pregnancy, childbirth, or breastfeeding. - Although significant, especially in resource-limited settings, global efforts and **PMTCT programs** have resulted in a significant reduction in this type of transmission. *Transmission via blood and blood products* - This mode was once a major concern but is now extremely rare in countries with robust **blood screening programs**. - While sharing contaminated needles among **intravenous drug users** remains a risk, transfusion-related HIV is largely controlled.

Practice by Chapter

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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