Infectious Diseases Practice Questions

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

> 2. ***> 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.

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

Hepatitis B. ***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.

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

Anopheles mosquitoes are known for transmitting malaria.. ***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.

Q: Human, animal, fomite or objects from which infective organism enters the host is called?

Source of infection. ***Source of infection*** - The **source of infection** refers to the person, animal, object, or substance from which an infectious agent passes immediately to a host. - This can include humans, animals, fomites, or contaminated objects that directly transmit the infectious organism. - This is the proximate source from which the agent enters the host. *Infective Reservoir* - An **infective reservoir** is the long-term habitat where an infectious agent normally lives, grows, and multiplies. - The reservoir can be human, animal, plant, soil, or inanimate matter where the agent is normally found. - While a reservoir can be a source, the source is specifically the immediate point from which transmission occurs. *Infective Carrier* - An **infective carrier** is an infected person or animal that harbors a specific infectious agent without showing clinical symptoms but can transmit it to others. - A carrier is a type of source (when transmission occurs from them), but the term "source" is broader, encompassing inanimate objects and fomites as well. *None of the above* - This option is incorrect because **Source of infection** accurately describes the concept presented in the question.

Q: Drug of choice for mass therapy under filariasis control programme?

DEC. ***Correct: DEC*** - **Diethylcarbamazine (DEC)** is the drug of choice for **mass drug administration (MDA)** campaigns aimed at eliminating lymphatic filariasis. - It effectively kills **microfilariae** and has some action on adult worms, reducing transmission. - In India's National Filariasis Elimination Programme, DEC is administered along with Albendazole in annual MDA campaigns. *Incorrect: Albendazole* - While **Albendazole** is co-administered with DEC in MDA programs, it is not the sole drug of choice for mass treatment of filariasis. - Its primary role is to provide **macrofilaricidal** activity (killing adult worms) and co-treatment for other helminth infections. - It enhances the effect of DEC but is not used alone. *Incorrect: Ivermectin* - **Ivermectin** is used in MDA programs for filariasis, particularly in areas co-endemic with **onchocerciasis** or where **Loa loa** is prevalent (as DEC is contraindicated in these areas). - However, in India and most lymphatic filariasis endemic areas, **DEC** remains the primary drug. *Incorrect: Mebendazole* - **Mebendazole** is an anthelminthic primarily used for treating **intestinal nematode infections** like ascariasis, trichuriasis, and hookworm. - It is **not used** in lymphatic filariasis mass treatment programs.

Q: Which of the following screening methods is primarily used under the National Tuberculosis Elimination Program (NTEP)?

Passive. ***Passive*** - Under the NTEP, **passive screening** involves individuals presenting to health facilities with symptoms suggestive of TB. - This method relies on **patient self-reporting** and healthcare provider suspicion, rather than active outreach. - Passive case finding is the **primary screening strategy** used across the general population in the NTEP framework. *Active* - **Active screening** involves community-based interventions to proactively identify individuals with TB, often in high-risk populations. - While active case finding is crucial for specific vulnerable groups (contacts, HIV patients, etc.), it is **not the primary screening method** under the standard NTEP framework for initial detection across the entire population. *Mass* - **Mass screening** involves testing large numbers of people in the general population, regardless of symptoms, to detect disease. - This is generally **cost-prohibitive** and not routinely implemented as a primary screening strategy for TB by the NTEP due to resource limitations and low yield in the general population. *None of the options* - **Passive screening** is indeed a primary method used under the NTEP, making this option incorrect. - The NTEP heavily relies on individuals seeking care when they experience symptoms, which aligns with the definition of passive case finding.

Q: Reservoir of infection in enteric fever?

Man. ***Man*** - Humans are the **sole natural reservoir** for *Salmonella Typhi* and *Salmonella Paratyphi*, the causative agents of enteric fever (typhoid and paratyphoid fever). - The bacteria can persist in the **gallbladder** of asymptomatic carriers, who can then shed the bacteria in their feces, contributing to transmission. *Birds* - Birds are not considered a primary reservoir for the **causative pathogens of enteric fever** (*Salmonella Typhi* or *Paratyphi*). - They are more commonly associated with other *Salmonella* serotypes, such as *Salmonella Enteritidis*, which cause **gastroenteritis** rather than systemic enteric fever. *Cow* - Cows are not a primary reservoir for the organisms responsible for **enteric fever**; these pathogens are specifically adapted to humans. - While cows can carry various *Salmonella* species, they are typically associated with **foodborne outbreaks** of *Salmonella*-induced **gastroenteritis**, not typhoid fever. *Water* - Water is a **vehicle for transmission** of enteric fever, becoming contaminated with human feces containing *Salmonella Typhi* or *Paratyphi*. - It is not a reservoir because the bacteria do not naturally **multiply or persist indefinitely** in water without a human source.

Q: What is the most common mode of transmission of HIV?

Sexual contact. ***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.

Question 1

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

Accepted Answer

> 2

Answer

< 1

Answer

< 2

Answer

> 1

Question 2

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

Accepted Answer

Hepatitis B

Answer

Measles

Answer

Rabies

Answer

Diphtheria

Question 3

Which of the following statements about pathogenic mosquitoes is correct?

Accepted Answer

Anopheles mosquitoes are known for transmitting malaria.

Answer

Mansonia mosquitoes lay their eggs in rafts.

Answer

Culex mosquitoes are primarily vectors for West Nile virus.

Answer

Aedes mosquitoes are known for their distinctive black and white striped markings.

Question 4

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

Accepted Answer

Person, animal or substance in which infectious agent lives and multiplies

Answer

Person, animal or object from which infectious agent is transmitted to host

Answer

Person or animal in which infectious agent causes a disease

Answer

Person or animal that transmits the infectious agent mechanically

Question 5

Which of the following statements about universal precautions is false?

Accepted Answer

Consider that all body fluids are contaminated with blood

Answer

Includes use of hand washing

Answer

Includes use of gloves and masks

Answer

To prevent transmission of blood borne pathogens

Question 6

Human, animal, fomite or objects from which infective organism enters the host is called?

Accepted Answer

Source of infection

Answer

Infective Reservoir

Answer

Infective Carrier

Answer

None of the above

Question 7

Drug of choice for mass therapy under filariasis control programme?

Accepted Answer

DEC

Answer

Albendazole

Answer

Ivermectin

Answer

Mebendazole

Question 8

Which of the following screening methods is primarily used under the National Tuberculosis Elimination Program (NTEP)?

Accepted Answer

Passive

Answer

Active

Answer

Mass

Answer

None of the options

Question 9

Reservoir of infection in enteric fever?

Accepted Answer

Man

Answer

Birds

Answer

Cow

Answer

Water

Question 10

What is the most common mode of transmission of HIV?

Accepted Answer

Sexual contact

Answer

Occupational exposure (needle stick injury)

Answer

Perinatal transmission (mother to child)

Answer

Transmission via blood and blood products

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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