Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 601: What is the PRIMARY indication for cholera vaccination according to WHO recommendations?

A. To control cholera outbreaks
B. For travelers to endemic regions
C. For individuals in endemic areas (Correct Answer)
D. For neonates at risk

Explanation: ***For individuals in endemic areas*** - **Cholera vaccination** is PRIMARY recommended by WHO for populations living in cholera-endemic areas as part of a comprehensive cholera prevention and control strategy. - This is the **most important indication** as it protects vulnerable populations with sustained high-risk exposure and can reduce disease burden in settings where cholera is a persistent public health problem. - WHO emphasizes integration with water, sanitation, and hygiene (WASH) improvements for maximum impact. *To control cholera outbreaks* - While cholera vaccination **can be used** during outbreaks (reactive vaccination), this is a secondary strategy. - The **primary outbreak control measures** remain: rapid case management, WASH interventions, surveillance, and contact tracing. - Vaccination during outbreaks faces logistical challenges and delayed protection (requires 2 doses, immunity takes time to develop). *For travelers to endemic regions* - Cholera vaccination **is recommended** for certain travelers to endemic areas, especially those with limited access to safe water/food. - However, this represents a **much smaller target population** compared to endemic area residents and is not the primary public health indication. - Most travelers have lower risk than residents and can protect themselves through food/water precautions. *For neonates at risk* - **Cholera vaccines are NOT recommended** for neonates (infants under 28 days). - Current oral cholera vaccines are only approved for children ≥1 year of age (varies by vaccine type). - Neonates have low cholera risk and are protected by maternal antibodies and caregiver hygiene practices.

Question 602: Chronic carriers of typhoid shed bacilli for how long after cure?

A. 1-3 weeks after cure
B. 3 weeks to 3 months after cure
C. 3 months - 1 year after cure
D. More than 1 year after cure (Correct Answer)

Explanation: ***More than 1 year after cure*** - A definition of a **chronic carrier** of *Salmonella Typhi (S. typhi)* is someone who excretes the bacteria in their feces or urine for **more than one year** after the acute illness. - This prolonged shedding is often associated with the presence of bacteria in the **gallbladder**, leading to intermittent fecal excretion. *1-3 weeks after cure* - This period typically represents the timeframe during which individuals are still considered **convalescent carriers** rather than chronic carriers. - Many patients continue to shed *S. typhi* for a few weeks post-treatment, but significant public health concern arises with more prolonged shedding. *3 weeks to 3 months after cure* - This timeframe is generally considered the period for **convalescent shedding**, where a significant number of individuals might still excrete *S. typhi*. - While concerning, it does not meet the established definition of a **chronic carrier**, which requires shedding for over a year. *3 months - 1 year after cure* - Individuals shedding *S. typhi* in their feces for this duration are at high risk of becoming **chronic carriers** or are in a prolonged state of convalescent carriage. - However, the official definition of a chronic carrier specifically requires shedding to persist **beyond one year**.

Question 603: Considering that dogs are the most common carriers of rabies and that the disease predominantly affects children in developing countries, what is the most effective and direct method to significantly reduce the incidence of rabies?

A. Conduct rabies testing for all dogs
B. Control the stray dog population and vaccinate all dogs (Correct Answer)
C. Enhance laboratory testing capabilities
D. Improve healthcare worker training for disease surveillance

Explanation: ***Control the stray dog population and vaccinate all dogs*** - As dogs are the primary reservoirs of rabies, controlling their population, coupled with widespread **dog vaccination**, is the most direct and effective strategy to break the transmission cycle to humans. - This approach tackles the root cause of the disease in areas where dog-mediated transmission is endemic, leading to a significant reduction in human rabies cases. *Conduct rabies testing for all dogs* - While testing identifies infected animals, it is **resource-intensive** and impractical for large dog populations, especially in low-resource settings, and does not prevent future infections. - This strategy is reactive rather than **proactive** in preventing the spread of rabies. *Enhance laboratory testing capabilities* - Improving laboratory testing capabilities is crucial for **surveillance** and accurate diagnosis but does not directly prevent rabies transmission at the source. - It's a supportive measure that helps monitor disease burden but isn't the most effective **primary intervention** for incidence reduction. *Improve healthcare worker training for disease surveillance* - Training healthcare workers enhances case detection and reporting, which is vital for **epidemiological monitoring** and timely post-exposure prophylaxis (PEP). - However, it does not address the fundamental issue of rabies transmission from dogs to humans and is not a direct prevention method for reducing disease incidence.

Question 604: Which strain was responsible for the most recent Influenza pandemic?

A. H1N1 (Correct Answer)
B. H5N1
C. H7N7
D. H3N2

Explanation: **Correct Option: H1N1** - The **H1N1 strain** of influenza virus was responsible for the **2009 swine flu pandemic**, which is considered the most recent global influenza pandemic. - This strain contained a unique combination of **influenza genes** not previously identified in animals or people, leading to widespread infection and human-to-human transmission. *Incorrect Option: H5N1* - **H5N1** is known for causing **avian influenza** (bird flu) and has occasionally infected humans, leading to severe disease and high mortality. - While it has epidemic potential, it has not caused a global pandemic with sustained human-to-human transmission. *Incorrect Option: H7N7* - **H7N7** is another avian influenza strain that has caused localized outbreaks in humans, primarily in those with close contact with infected birds. - It has not led to a widespread human pandemic. *Incorrect Option: H3N2* - **H3N2** is a common seasonal influenza strain that causes annual epidemics and has been responsible for past pandemics (e.g., the **1968 Hong Kong Flu**). - However, it was not the strain responsible for the most recent influenza pandemic in 2009.

Question 605: Which of the following statements regarding Japanese encephalitis is false?

A. Humans are dead-end hosts
B. Transmitted by culex
C. Caused by flavivirus
D. Cattle are amplifier hosts (Correct Answer)

Explanation: ***Cattle are amplifier hosts*** - Cattle are generally **not considered amplifier hosts** for Japanese encephalitis virus (JEV); instead, **pigs and wading birds** serve as primary amplifier hosts. - Amplifier hosts are crucial for **maintaining and spreading the virus** in the environment, leading to increased transmission to mosquito vectors. *Caused by flavivirus* - This statement is true; Japanese encephalitis virus (JEV) is indeed a **mosquito-borne flavivirus**, belonging to the *Flaviviridae* family. - Other notable flaviviruses include **Dengue, Zika, and West Nile viruses**. *Humans are dead-end hosts* - This statement is true; humans are considered **dead-end hosts** for JEV because the viremia levels achieved in infected humans are generally too low to infect mosquitoes. - Therefore, humans **do not contribute significantly to the transmission cycle** of the virus among mosquito vectors and other hosts. *Transmitted by culex* - This statement is true; Japanese encephalitis is primarily transmitted by **mosquitoes of the *Culex* genus**, especially *Culex tritaeniorhynchus*. - These mosquitoes typically **breed in rice paddies** and other agricultural areas.

Question 606: Vector for Zika virus is:

A. Aedes (Correct Answer)
B. Culex
C. Anopheles
D. None of the options

Explanation: ***Aedes*** - The **Aedes mosquito** species, particularly *Aedes aegypti* and *Aedes albopictus*, is the primary vector for the transmission of the **Zika virus**. - These mosquitoes are also known vectors for other arboviruses, such as **Dengue** and **Chikungunya**. - **Aedes** mosquitoes are day-biting mosquitoes that breed in clean, stagnant water. *Culex* - **Culex mosquitoes** are the primary vectors for diseases like **West Nile virus** and **Japanese encephalitis**. - While *Culex* mosquitoes can occasionally carry the Zika virus in laboratory settings, they are not considered significant vectors for human transmission in nature. - These are primarily **night-biting** mosquitoes. *Anopheles* - **Anopheles mosquitoes** are the sole vectors responsible for transmitting **malaria parasites** to humans. - They do not play a significant role in the transmission of the Zika virus or other arboviral diseases. - These are also **night-biting** mosquitoes with a characteristic resting posture. *None of the options* - This option is incorrect because the **Aedes mosquito** is a well-established and recognized vector for the Zika virus. - The mode of transmission for Zika virus is primarily through mosquito bites, with identified vectors belonging to the *Aedes* genus.

Question 607: In the context of public health administration in India, which of the following health-related matters is included in the Concurrent List of the Indian Constitution?

A. International immigration rule for quarantine
B. Mines and oilfield workers rules
C. Establishment and maintenance of drug standards
D. Prevention of communicable diseases from one unit to another (Correct Answer)

Explanation: **Prevention of communicable diseases from one unit to another** - This falls under the **Concurrent List** (List III, Entry 29 of the Seventh Schedule) of the Indian Constitution, allowing both the Central and State governments to legislate on matters of preventing the extension of infectious or contagious diseases or pests from one State to another. - The shared responsibility is crucial for effective **disease control** and ensures coordinated public health responses across state boundaries. *International immigration rule for quarantine* - Rules governing **international immigration and quarantine** (Entry 81) are exclusively listed under the **Union List** (List I), meaning only the Central Government can legislate on these matters. - This centralization ensures uniform standards for **border health control** and international travel. *Mines and oilfield workers rules* - The regulation of **labor and safety in mines, oilfields, and major ports** (Entry 55) is primarily under the **Union List**, granting the Central Government legislative authority. - This ensures consistent **safety standards** and worker protection in these critical sectors nationwide. *Establishment and maintenance of drug standards* - The establishment of **standards for drugs** and other vital goods (Entry 33) is primarily a Union responsibility and falls under the **Union List**, promoting uniformity in product quality and safety across the country. - This centralized control ensures that essential items like medicines meet a consistent benchmark for **quality control** and public safety.

Question 608: Kala-Azar is found in all endemic areas except for which of the following?

A. Uttar Pradesh
B. Himachal Pradesh (Correct Answer)
C. West Bengal
D. Bihar

Explanation: ***Himachal Pradesh*** - **Kala-azar (visceral leishmaniasis)** is endemic to specific regions in India, primarily the Gangetic plains. - Himachal Pradesh is a **non-endemic state** for kala-azar, differentiating it from the other options. *West Bengal* - West Bengal is one of the **highly endemic states** for kala-azar in India due to favorable environmental and socioeconomic conditions for the sandfly vector. - It has a significant burden of the disease, particularly in its northern and central districts. *Uttar Pradesh* - Uttar Pradesh is another **endemic state** for kala-azar, particularly the eastern parts bordering Bihar. - The disease is prevalent in districts along the Ganges river basin, contributing to the overall disease burden in India. *Bihar* - Bihar is considered the **most highly endemic state** for kala-azar in India, accounting for a large proportion of cases. - High poverty, poor housing, and a suitable environment for the sandfly vector contribute to its significant prevalence in the state.

Question 609: Contact isolation is done for

A. Mumps
B. Asthma
C. Diphtheria
D. MRSA (Correct Answer)

Explanation: ***MRSA*** - **Methicillin-resistant *Staphylococcus aureus* (MRSA)** is transmitted primarily through direct contact with infected patients or contaminated surfaces, necessitating **contact isolation**. - **Contact precautions** involve the use of **gloves** and **gowns** when entering the patient's room to prevent transmission. *Mumps* - Mumps is a viral infection that is primarily transmitted via **respiratory droplets** produced during coughing, sneezing, or talking. - Patients with mumps typically require **droplet isolation**, not contact isolation, to prevent airborne transmission. *Diphtheria* - Diphtheria is a bacterial infection spread through **respiratory droplets** from the nose and throat of an infected person. - **Droplet precautions** are generally recommended for diphtheria, involving masks within a certain distance, rather than contact isolation. *Asthma* - **Asthma** is a chronic inflammatory condition of the airways and is not an infectious disease. - As asthma is not transmissible, it does **not require any form of isolation precautions** (contact, droplet, or airborne).

Question 610: Which of the following is an example of indirect transmission in communicable diseases?

A. Sexually transmitted diseases (STDs)
B. Transplacental transmission
C. Soil-borne transmission (Correct Answer)
D. Respiratory droplet transmission

Explanation: ***Soil-borne transmission*** - This involves an **intermediate vehicle** (soil) contaminated with infectious agents, facilitating transmission without direct host-to-host contact. - Diseases like **tetanus** (Clostridium tetani spores) and **hookworm infections** are classic examples where contaminated soil acts as a reservoir. *Transplacental transmission* - This is a form of **vertical transmission**, where the infectious agent passes directly from mother to fetus via the placenta. - It is considered a form of **direct transmission** as there is no external intermediary. *Sexually transmitted diseases (STDs)* - These are typically transmitted through **direct person-to-person contact** during sexual activity. - This is a clear example of **direct transmission**, involving close physical contact between individuals. *Respiratory droplet transmission* - This occurs when droplets expelled from an infected person's respiratory tract land on the mucous membranes of a susceptible person. - While it involves airborne particles, it's generally considered a form of **direct transmission** when the droplets travel a short distance, or in some contexts, can bridge to an indirect form if they settle on surfaces before contact.

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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