Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 571: What is the vector responsible for transmitting dengue fever?

A. Anopheles mosquito
B. Aedes mosquito (Correct Answer)
C. Culex mosquito
D. Sandfly

Explanation: ***Aedes mosquito*** - The **Aedes aegypti** and **Aedes albopictus** mosquitoes are the primary vectors for transmitting the dengue virus. - These mosquitoes are characterized by their **distinctive black and white markings** on their bodies and legs. *Anopheles mosquito* - The **Anopheles mosquito** species are the primary vectors for transmitting **malaria**. - They are also known to transmit **lymphatic filariasis** in some regions. *Culex mosquito* - **Culex mosquitoes** are known vectors for various arboviruses, including **West Nile virus**, **Japanese encephalitis**, and **St. Louis encephalitis**. - They can also transmit **lymphatic filariasis** and **avian malaria**. *Sandfly* - **Sandflies** are responsible for transmitting **leishmaniasis**, a parasitic disease. - They are also vectors for **sandfly fever (Phlebotomus fever)** and **Bartonellosis**.

Question 572: What is the main objective of the National AIDS Control Program?

A. To provide financial support to patients with HIV/AIDS
B. To prevent the transmission of HIV and reduce associated morbidity and mortality (Correct Answer)
C. To promote the use of antiretroviral drugs in the general population
D. To conduct research on HIV/AIDS vaccines

Explanation: ***To prevent the transmission of HIV and reduce associated morbidity and mortality*** - The core mission of the **National AIDS Control Program (NACP)** is to prevent new HIV infections and mitigate the impact of the epidemic by reducing illness and death among those affected. - This objective is achieved through comprehensive strategies including awareness campaigns, testing, treatment, and care services. *To provide financial support to patients with HIV/AIDS* - While patient support is a component of comprehensive care, direct **financial support** is not the *main objective* of the NACP, which focuses more broadly on public health intervention. - Financial aid might be offered through specific schemes or NGOs, but it's not the primary, overarching goal of the national program. *To promote the use of antiretroviral drugs in the general population* - **Antiretroviral drugs (ARVs)** are crucial for treating HIV-positive individuals and preventing mother-to-child transmission, but promoting their use in the *general population* (i.e., among uninfected individuals) is not a goal. - Their use is generally restricted to treatment, post-exposure prophylaxis (PEP), and pre-exposure prophylaxis (PrEP) for specific high-risk groups. *To conduct research on HIV/AIDS vaccines* - While vaccine research is vital in the global fight against HIV, it is typically undertaken by specialized **research institutions** and pharmaceutical companies. - The NACP's primary role is focused on implementing public health programs and policies rather than direct scientific research and vaccine development.

Question 573: A 2-year-old child presents with a rash and fever. He is diagnosed with measles. What is the most likely period of communicability for this disease?

A. 1-2 days before to 4-5 days after appearance of rash
B. 3-4 days before to 3-4 days after appearance of rash (Correct Answer)
C. 2-3 days before to 5-6 days after appearance of rash
D. 5-6 days before to 1-2 days after appearance of rash

Explanation: ***3-4 days before to 3-4 days after appearance of rash*** - Measles is **highly contagious**, and infected individuals can spread the virus from approximately **4 days before the onset of rash** (prodromal phase). - The period of communicability extends up to **4 days after the rash appears**, making **isolation crucial** during this entire period. - This option most closely reflects the **CDC and WHO guidelines** which state communicability from 4 days before to 4 days after rash onset. - The **prodromal phase** (catarrhal stage with cough, coryza, conjunctivitis) is when the patient is most infectious. *1-2 days before to 4-5 days after appearance of rash* - This option **significantly underestimates** the pre-rash communicability period. - Measles virus is shed during the **entire prodromal phase**, which typically begins 2-4 days before rash and lasts 2-4 days. - Stating only 1-2 days before would lead to **inadequate isolation measures** and increased disease transmission. *2-3 days before to 5-6 days after appearance of rash* - While this extends appropriately into the post-rash period, it still **underestimates the critical pre-rash communicability**. - The 5-6 days after rash is slightly longer than standard teaching, though immunocompromised patients may remain infectious longer. *5-6 days before to 1-2 days after appearance of rash* - This option correctly recognizes extended pre-rash communicability but **severely underestimates post-rash transmission**. - Patients remain highly contagious for at least 4 days after rash appearance, not just 1-2 days. - This would result in **premature discontinuation of isolation** and nosocomial transmission.

Question 574: A traveler returning from South America presents with fever, jaundice, and muscle pain. Serology confirms the presence of antibodies against the yellow fever virus. What is the primary vector of this virus?

A. Aedes mosquito (Correct Answer)
B. Anopheles mosquito
C. Culex mosquito
D. Ixodes tick

Explanation: ***Aedes mosquito*** - **Aedes aegypti** is the **primary vector for yellow fever virus**, responsible for transmission in both urban (Aedes aegypti) and jungle/sylvatic (Aedes species) cycles - This mosquito is prevalent in **tropical and subtropical regions including South America**, where yellow fever is endemic - The clinical triad of **fever, jaundice, and muscle pain** is characteristic of yellow fever infection - Aedes mosquitoes also transmit other arboviruses including **Dengue**, **Chikungunya**, and **Zika** viruses *Anopheles mosquito* - The **Anopheles mosquito** is the primary vector for **malaria** (caused by *Plasmodium* species), not yellow fever - Clinical presentation of malaria includes fever with chills and rigors, but typically without the severe jaundice seen in yellow fever - Also transmits **lymphatic filariasis** caused by filarial worms *Culex mosquito* - **Culex mosquitoes** transmit **Japanese encephalitis**, **West Nile virus**, and **St. Louis encephalitis** - These are neurotropic viruses causing encephalitis, not the hepatotropic manifestations (jaundice) seen in yellow fever - Also involved in transmission of **lymphatic filariasis** *Ixodes tick* - **Ixodes ticks** are arthropod vectors (not mosquitoes) that transmit **Lyme disease** (*Borrelia burgdorferi*) and **Babesiosis** (*Babesia* species) - Also transmit **Anaplasmosis** and **Powassan virus** - Not associated with arboviral hemorrhagic fevers like yellow fever

Question 575: Which type of hepatitis virus is most commonly transmitted through contaminated food and water?

A. Hepatitis A (Correct Answer)
B. Hepatitis B
C. Hepatitis C
D. Hepatitis E

Explanation: ***Hepatitis A*** - **Hepatitis A virus (HAV)** is primarily transmitted via the **fecal-oral route**, which includes the consumption of contaminated food and water. - This is the **most common** hepatitis virus transmitted through contaminated food and water **globally**. - Common in areas with **poor sanitation** and responsible for **widespread outbreaks** worldwide, particularly through contaminated food handling. - HAV is highly endemic in developing countries and accounts for the majority of acute viral hepatitis cases transmitted via food and water. *Hepatitis B* - **Hepatitis B virus (HBV)** is mainly transmitted through contact with infected **blood, semen, or other bodily fluids**. - Common routes include sexual contact, sharing needles, and mother-to-child transmission during birth. - **Not transmitted** through food or water. *Hepatitis C* - **Hepatitis C virus (HCV)** is most commonly spread through contact with infected **blood**, primarily via sharing needles among injecting drug users. - Other transmission routes include contaminated blood transfusions (prior to screening) and less commonly, sexual contact. - **Not transmitted** through food or water. *Hepatitis E* - **Hepatitis E virus (HEV)** is also transmitted via the fecal-oral route through **contaminated water and undercooked meat** (especially pork). - While HEV can cause waterborne outbreaks, particularly in **South Asia**, Hepatitis A remains more prevalent globally as a foodborne/waterborne pathogen. - HEV is more commonly associated with large waterborne epidemics in specific regions, whereas HAV has broader geographic distribution and higher overall incidence via food and water contamination.

Question 576: How is Hepatitis A primarily transmitted?

A. Sexual contact
B. Blood transfusion
C. Fecal-oral route (Correct Answer)
D. Respiratory droplets

Explanation: ***Fecal-oral route*** - Hepatitis A virus (HAV) is primarily transmitted through the **ingestion of food or water contaminated with fecal matter** from an infected person. - This route is common in areas with poor sanitation and hygiene practices. *Sexual contact* - While possible, sexual transmission of Hepatitis A is **less common** than fecal-oral transmission and typically involves oral-anal contact. - **Hepatitis B and C** are more frequently associated with sexual transmission. *Blood transfusion* - Hepatitis A transmission through blood transfusion is **rare** because the virus is typically found in the blood for a short period during the acute phase of infection. - **Hepatitis B, C, and retroviruses (like HIV)** are the classic risks associated with blood transfusions. *Respiratory droplets* - Transmission via respiratory droplets is typical for viruses that affect the respiratory system, such as **influenza** or **COVID-19**. - Hepatitis A is an **enteric virus** and does not spread through the air.

Question 577: A health campaign aims to reduce the incidence of HIV in a high-prevalence area. Which combination of strategies is most likely to be effective?

A. Condom distribution and needle exchange programs (Correct Answer)
B. Public awareness campaigns and abstinence education
C. Antiretroviral therapy and nutritional support
D. Routine screening and treatment of STIs

Explanation: ***Condom distribution and needle exchange programs*** - These strategies directly target the **main modes of HIV transmission**: unprotected sexual activity and sharing contaminated needles. - **Condoms** provide a barrier against sexual transmission, while **needle exchange programs** reduce the spread through intravenous drug use. - These are **primary prevention tools** that can be deployed broadly to uninfected populations in high-prevalence areas to reduce new infections (incidence). - Evidence-based approach endorsed by **WHO, UNAIDS, and CDC** for population-level HIV prevention. *Public awareness campaigns and abstinence education* - **Public awareness campaigns** are important for general knowledge but may not translate to behavior change without concrete prevention tools. - **Abstinence-only education** has limited effectiveness in diverse populations and does not equip individuals with skills for safer practices when abstinence is not maintained. - Lacks the direct barrier protection offered by Option A. *Antiretroviral therapy and nutritional support* - **Antiretroviral therapy (ART)** is crucial for treating HIV-positive individuals and plays a key role in **Treatment as Prevention (TasP)** by reducing viral load to undetectable levels (U=U). - However, for **reducing incidence** in a high-prevalence area, ART primarily benefits those already infected and requires knowing HIV status through testing. - It does not provide **primary prevention** for the uninfected majority in the population, unlike condoms and needle exchange which can be distributed broadly. - **Nutritional support** is vital for the health of infected individuals but does not prevent HIV acquisition. - While important for treatment and secondary prevention, this combination is less effective than Option A for reducing new infections at the population level. *Routine screening and treatment of STIs* - **Routine screening and treatment of STIs** reduce co-factors that increase HIV transmission risk (e.g., genital ulcers enhance susceptibility). - This is a **secondary prevention approach** that indirectly reduces transmission risk. - While valuable as part of comprehensive HIV prevention, it does not directly prevent the primary modes of HIV transmission as effectively as barrier methods or harm reduction strategies.

Question 578: At what temperature and duration is pasteurization typically done?

A. 73 °C for 20 minutes
B. 63 °C for 30 minutes (Correct Answer)
C. 72 °C for 30 seconds
D. 63 °C for 30 seconds

Explanation: ***63 °C for 30 minutes*** - This temperature and duration represent the **batch pasteurization method** (also known as low-temperature long-time or LTLT pasteurization), commonly used for smaller volumes of milk. - This method is effective in killing common pathogens like *Mycobacterium tuberculosis* and *Coxiella burnetii* while largely preserving the nutritional quality and flavor of the milk. - This is the **classic definition** of pasteurization and remains widely taught in medical curricula. *73 °C for 20 minutes* - This temperature and duration are **not a recognized standard** for any pasteurization method. - This would unnecessarily over-process the milk, degrading heat-sensitive nutrients and affecting organoleptic properties without additional microbial safety benefits. *72 °C for 30 seconds* - This is **not the standard HTST method** (which uses 72°C for **15 seconds**, not 30 seconds). - While 72°C is the correct temperature for high-temperature short-time (HTST) pasteurization, the duration of 30 seconds is double the standard time, making this a non-standard specification. - The standard HTST method (72°C/15sec) is widely used for continuous flow processing of large volumes. *63 °C for 30 seconds* - This duration is **too short** for the given temperature to be effective in killing all target pathogens. - A temperature of 63°C requires a longer holding time (30 minutes) to achieve adequate microbial reduction, as in the LTLT method.

Question 579: Infectivity of convalescent carrier of cholera lasts for?

A. 1-5 days
B. 1-2 weeks
C. 2-3 weeks (Correct Answer)
D. 4-5 weeks

Explanation: ***2-3 weeks*** - The infectivity of a **convalescent carrier** of cholera typically lasts for about **2 to 3 weeks** after recovery, according to **Park's Textbook of Preventive and Social Medicine**. - During this period, individuals can still shed **Vibrio cholerae** in their feces, posing a risk of transmission. - This is the **standard duration** taught in Indian medical education for examination purposes. *1-5 days* - This timeframe is too short for the infectivity of a **convalescent carrier**, as bacterial shedding extends well beyond the acute phase. - While symptoms may resolve within this period, the organism continues to be excreted for much longer. *1-2 weeks* - While many individuals may stop shedding within this period (per WHO/CDC data), for examination purposes, the convalescent carrier period is defined as **2-3 weeks**. - This option represents the **lower range** but underestimates the full duration taught in standard Indian textbooks. *4-5 weeks* - This period is too long for the typical infectivity duration of a **convalescent carrier** of cholera. - **Chronic carriers** (rare in cholera, <1% of cases) can shed for months, but this does not represent the convalescent carrier period.

Question 580: What type of approach does the colored kit for STD treatment represent?

A. Preventive
B. Symptomatic
C. Syndromic (Correct Answer)
D. Rehabilitative

Explanation: ***Syndromic*** - A **syndromic approach** to STD treatment involves managing patients based on the **symptoms** they present, rather than waiting for laboratory confirmation of specific pathogens. - The colored kit likely provides a pre-packaged set of medications to treat the most common causes of a particular STD syndrome, allowing for rapid and effective treatment without relying on complex diagnostics. *Preventive* - **Preventive approaches** aim to avert the occurrence of disease through measures like **vaccination**, safe sex education, and condom distribution. - While treating STDs has a secondary preventive effect by reducing transmission, the colored kit itself is a treatment tool, not primarily a preventive measure. *Symptomatic* - While the syndromic approach *uses* symptoms, the term **symptomatic** treatment typically refers to relieving symptoms without necessarily addressing the underlying cause or making a specific diagnosis. - The colored kit aims to treat the suspected *cause* of the syndrome, not just palliate symptoms, distinguishing it from purely symptomatic management. *Rehabilitative* - **Rehabilitative approaches** focus on restoring function and quality of life after an illness or injury, often involving therapies and long-term care. - STD treatment is acute and aims to cure the infection, which is distinctly different from rehabilitation.

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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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