Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 681: Which disease is NOT primarily transmitted by hard ticks?

A. KFD
B. Indian tick typhus
C. Tularemia
D. Relapsing fever (Correct Answer)

Explanation: ***Relapsing fever*** - Relapsing fever, particularly **epidemic louse-borne relapsing fever**, is primarily transmitted by the human body louse (*Pediculus humanus humanus*), not hard ticks. - While some forms of relapsing fever (endemic relapsing fever) *can* be transmitted by soft ticks, the most common association for public health concern regarding relapsing fever is with lice. *KFD* - **Kyasanur Forest Disease (KFD)** is a viral hemorrhagic fever transmitted by the bite of **hard ticks**, primarily *Haemaphysalis spinigera*. - The disease is endemic to certain regions of India and is a classic example of a hard tick-borne illness. *Indian tick typhus* - **Indian tick typhus** is a form of **spotted fever group rickettsiosis** caused by *Rickettsia conorii*, which is transmitted by **hard ticks**, including *Rhipicephalus sanguineus* (brown dog tick). - It is a well-known tick-borne disease in tropical and subtropical regions. *Tularemia* - While tularemia can be transmitted by various routes, **hard ticks** such as *Dermacentor* (dog ticks) and *Amblyomma* (lone star ticks) are important vectors for transmitting *Francisella tularensis*. - Tick bites are a significant mode of transmission for the **ulceroglandular form** of tularemia.

Question 682: Which of the following waterborne diseases is characterized by rice water stools?

A. Giardiasis
B. Typhoid fever
C. Cholera (Correct Answer)
D. Hepatitis A

Explanation: ***Typhoid fever*** - **Rice water stools** are a classic symptom of **cholera**, not typhoid fever. Typhoid fever is characterized by a **step-ladder fever pattern**, **bradycardia**, and abdominal pain, eventually leading to a rose-spot rash. - The causative agent of typhoid fever is **Salmonella typhi**, which primarily invades the gastrointestinal tract and then disseminates systemically. *Giardiasis* - Giardiasis is caused by the parasite **Giardia lamblia**, and its typical symptoms include **fatty**, **foul-smelling stools**, **bloating**, cramps, and weight loss, not rice water stools. - This infection is often acquired through the ingestion of **cysts** from contaminated water or food. *Cholera* - **Cholera** is the correct answer and is classically characterized by the production of **massive watery diarrhea** with **“rice water” stools**, which are gray, turbid, and flecked with mucus. - This severe dehydration is due to the action of **cholera toxin**, which causes electrolyte and fluid secretion into the intestinal lumen. *Hepatitis A* - **Hepatitis A** is primarily a **viral liver infection** characterized by **jaundice**, dark urine, fatigue, and nausea, and it does not typically present with diarrhea, especially not rice water stools. - It is transmitted via the **fecal-oral route**, often through contaminated food or water, but its primary target is the liver.

Question 683: Which of the following is not included in the Revised National Tuberculosis Control Programme (RNTCP)?

A. Chest X-rays are used as a diagnostic tool for tuberculosis.
B. Directly observed therapy (DOT) is a key strategy in tuberculosis control.
C. Active case finding is a strategy used in tuberculosis control. (Correct Answer)
D. Daily drug administration is part of the tuberculosis treatment regimen.

Explanation: ***Active case finding is a strategy used in tuberculosis control*** - **This is the correct answer** - Traditional RNTCP primarily relied on **passive case finding**, where symptomatic patients self-report to health facilities - While active case finding (systematic screening of high-risk groups) is now emphasized in NTEP (National TB Elimination Programme), it was **not a major strategy in the original RNTCP framework** - The classic RNTCP approach focused on identifying patients who presented with symptoms rather than actively seeking cases in the community *Directly observed therapy (DOT) is a key strategy in tuberculosis control* - **DOT is a cornerstone** of RNTCP/NTEP to ensure treatment adherence - A trained provider directly observes the patient taking anti-TB medications - This prevents treatment default and reduces drug resistance *Chest X-rays are used as a diagnostic tool for tuberculosis* - **Chest X-rays are integral** to RNTCP for screening and diagnosis of pulmonary TB - Used in conjunction with sputum microscopy/molecular tests like CBNAAT - Helps identify lung involvement and assess disease severity *Daily drug administration is part of the tuberculosis treatment regimen* - **RNTCP/NTEP uses daily drug regimens** for most TB categories (replaced older intermittent regimens) - Daily dosing improves treatment efficacy and patient adherence - Part of the standardized treatment protocols under the programme

Question 684: Which of the following is a reservoir for measles?

A. Man (Correct Answer)
B. Soil
C. Fomites
D. Monkey

Explanation: ***Man*** - Humans are the **natural and sole reservoir** for the measles virus (**Morbillivirus**). - The virus is highly contagious and spreads directly from person to person via respiratory droplets. *Soil* - Soil is a reservoir for certain **bacterial or fungal pathogens** (e.g., *Clostridium tetani*, *Histoplasma capsulatum*), but not for measles virus. - Viruses, especially those causing human-specific diseases like measles, do not typically survive or replicate in soil. *Fomites* - Fomites are **inanimate objects** that can harbor pathogens and contribute to transmission. - While measles virus can survive on fomites for a short period, they are a mode of transmission, not a reservoir where the virus multiplies or is maintained. *Monkey* - Monkeys are reservoirs for some viruses (e.g., simian immunodeficiency virus), but not for the **measles virus**. - Measles is a **human-specific disease**, and while some closely related viruses can affect primates, monkeys do not naturally harbor or transmit human measles.

Question 685: In the context of a viral outbreak, what is the first step that public health officials should take?

A. Immunization
B. Notification (Correct Answer)
C. Isolation
D. Verification of diagnosis

Explanation: ***Correct: Notification*** - **Notification** is the **first and essential step** in public health outbreak management as mandated by the International Health Regulations (IHR) and national disease surveillance systems - Immediate notification to public health authorities triggers the entire surveillance and response mechanism, enabling coordinated investigation, resource mobilization, and implementation of control measures - Without notification, the public health system cannot mount an organized response, and individual isolation efforts remain uncoordinated and potentially ineffective - Notification activates the epidemic response teams who then conduct verification, implement isolation, and coordinate other control measures *Incorrect: Isolation* - While **isolation** is a critical containment measure, it cannot be the first step before cases are identified and reported through the surveillance system - Isolation is implemented **after** notification and during/after case verification as part of the coordinated public health response - Premature isolation without proper notification leads to fragmented, uncoordinated responses and missed opportunities for comprehensive outbreak control *Incorrect: Verification of diagnosis* - **Verification of diagnosis** is essential but occurs **after** notification to health authorities - The verification process (epidemiological investigation and laboratory confirmation) is conducted by public health teams mobilized through the notification system - While clinical suspicion may exist, formal verification requires coordinated investigation that follows notification *Incorrect: Immunization* - **Immunization** is a preventive and control measure implemented in later stages of outbreak response - Vaccine deployment requires significant planning, availability, and logistics that can only be coordinated after the outbreak is officially reported and verified - Ring vaccination or mass immunization campaigns are organized interventions that follow the initial notification and assessment phases

Question 686: All of the following diseases can be eradicated, EXCEPT:

A. Guinea worm
B. Polio
C. Tuberculosis (Correct Answer)
D. Measles

Explanation: ***Tuberculosis*** - **Tuberculosis** is extremely difficult to eradicate due to its airborne transmission, ability to lie **latent** in carriers, and the emergence of **drug-resistant strains**. - Widespread reservoirs of infection and the lack of a fully effective vaccine make complete eradication highly challenging. *Guinea worm* - Guinea worm disease (Dracunculiasis) is close to eradication due to its unique life cycle, which involves only **human hosts** and **copepods (water fleas)** as intermediate hosts. - Eradication efforts focus on simple interventions like **filtering drinking water** and preventing contaminated water consumption. *Polio* - Polio is targeted for eradication due to the availability of effective **oral and inactivated vaccines** and the fact that the poliovirus has no animal reservoir, only infecting humans. - Global vaccination campaigns have dramatically reduced its incidence, with only a few endemic countries remaining. *Measles* - Measles is a prime candidate for eradication because humans are the virus's only natural host, and a highly effective, **live-attenuated vaccine** provides long-lasting immunity. - High vaccination coverage can interrupt transmission and has led to elimination in many regions.

Question 687: Gap in the time interval between the onset of the primary and secondary case is

A. Serial interval (Correct Answer)
B. Generation time
C. Onset period
D. Incubation period

Explanation: ***Serial interval*** - The **serial interval** directly measures the time elapsed between the onset of symptoms in a primary case and the onset of symptoms in a secondary case infected by the primary case. - This metric is crucial for understanding the **speed of pathogen transmission** within a population. *Generation time* - **Generation time** refers to the period between infection in a primary case and infection in a secondary case, which is difficult to observe directly. - While related to the serial interval, it specifically focuses on **infection events** rather than symptom onset. *Onset period* - **Onset period** is not a standard epidemiological term for the time gap between primary and secondary cases. - It might vaguely refer to the time from exposure to symptom onset but lacks the specific context of **transmission dynamics**. *Incubation period* - The **incubation period** is the time between exposure to an infectious agent and the onset of symptoms in a single individual. - It does not involve the **transmission event** between a primary and a secondary case.

Question 688: Which of the following diseases requires airborne isolation with negative pressure rooms for the longest duration during active infection?

A. Cholera (severe cases)
B. Measles (during outbreaks)
C. Influenza
D. Tuberculosis (Correct Answer)

Explanation: ***Tuberculosis*** - Requires **prolonged airborne isolation** in negative pressure rooms, often for **weeks to months** until the patient is no longer infectious (typically after 2-3 weeks of effective treatment and sputum conversion). - Patients with **active pulmonary TB** remain infectious for an extended period and require strict airborne precautions to prevent transmission through aerosol droplets. - TB isolation is among the most **rigorous and prolonged** compared to other infectious diseases due to its chronic nature and high transmissibility. *Cholera (severe cases)* - Requires **enteric/contact precautions** rather than airborne isolation. - Spreads through **fecal-oral route** via contaminated water and food. - Isolation duration is typically **shorter** (3-5 days) and focuses on sanitation and fluid management rather than airborne precautions. *Measles (during outbreaks)* - Does require **airborne isolation** due to high contagiousness via respiratory droplets. - However, isolation period is **much shorter** than TB—typically **4 days after rash onset** (or until immune recovery in immunocompromised). - Once the infectious period ends, isolation can be discontinued relatively quickly compared to TB. *Influenza* - Requires **droplet and contact precautions**, not strict airborne isolation for most strains. - Isolation period is **short** (typically **5-7 days** from symptom onset, or 24 hours after fever resolution with antivirals). - Standard surgical masks and droplet precautions are usually sufficient, unlike the N95 respirators and negative pressure rooms required for TB.

Question 689: Which of the following statements about measles is incorrect?

A. Secondary attack rate is 90%
B. Maximum incidence in 6 months to 3 years age group
C. Best age for immunization is 9-12 months
D. Secondary attack rate is 30% (Correct Answer)

Explanation: ***Secondary attack rate is 30%*** - Measles is highly contagious, and its **secondary attack rate** is much higher than 30%, often reaching **90% or more** among susceptible household contacts. - A 30% secondary attack rate would be exceptionally low for a disease with measles's known **high transmissibility**. *Maximum incidence in 6 months to 3 years age group* - This statement is correct as **maternal antibodies wane** around 6 months, making infants susceptible, and young children in this age range are often actively exposed in community settings. - Peak incidence occurs in this age group, particularly in **unvaccinated or under-vaccinated populations**. *Best age for immunization is 9-12 months* - This is the **recommended age** for measles vaccination under India's **Universal Immunization Programme (UIP)**. - Immunizing at this age ensures that waning maternal antibodies do not interfere with vaccine efficacy while providing timely protection during the high-risk period. *Secondary attack rate is 90%* - This statement is correct. Measles is one of the **most contagious infectious diseases**, with a secondary attack rate among susceptible household contacts often **exceeding 90%**. - Its high transmissibility is due to its **airborne spread** and long communicable period.

Question 690: In the context of malaria management, surveillance every fortnight is part of which specific programme?

A. Urban malaria scheme
B. National malaria control programme
C. Modified plan of operation (Correct Answer)
D. Malaria eradication programme

Explanation: ***Modified plan of operation*** - The Modified Plan of Operation (MPO), launched in **1977**, introduced **active surveillance every fortnight** with house-to-house visits and presumptive treatment - This was the **defining characteristic** of MPO, aimed at containing perennial malaria transmission in areas where eradication failed - Objective: Reduce the Slide Positive Incidence Rate (SPIR) to **less than 2%**, indicating a strategy of control rather than eradication - Fortnightly surveillance distinguished MPO from all previous malaria programmes in India *Urban malaria scheme* - Focuses on malaria control specifically in **urban areas** with anti-larval operations and targeted case management - Does **not mandate fortnightly surveillance** as its defining characteristic - Part of broader malaria control efforts rather than a programme defined by specific surveillance frequency *National malaria control programme* - Initiated in **1953**, focused on reducing morbidity and mortality through **indoor residual spraying (IRS)** - Did **not implement fortnightly surveillance** as its primary strategy - Later replaced by National Malaria Eradication Programme (NMEP) in 1958 due to initial success *Malaria eradication programme* - Launched in **1958**, aimed for complete elimination through extensive residual insecticide spraying - Used **passive case detection** rather than active fortnightly house-to-house surveillance - Did not specify fortnightly surveillance with presumptive treatment like the MPO did after disease resurgence

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