Infectious Diseases Practice Questions

Q: H5N1 Avian influenza has not become an epidemic till now. What is the most important reason for this?

Human to human transmission is rare. ***Human to human transmission is rare*** - While H5N1 can infect humans, its **limited ability to spread efficiently from person to person** is the primary reason it has not caused a human pandemic. - Efficient human-to-human transmission is a prerequisite for any widespread epidemic or pandemic. *Seen only in wild birds and not in domestic poultry* - H5N1 can affect both **wild birds and domestic poultry**, contradicting the statement. - The virus's presence in domestic poultry has historically been a significant source of human exposure. *It causes serious illness leading to death of the patient* - The **severity of illness and high mortality rate** in infected humans actually makes epidemic control more challenging, not less, if human-to-human transmission were efficient. - However, this characteristic alone does not prevent the virus from becoming an epidemic unless it can spread between people. *It has avian influenza genes* - The presence of avian influenza genes is simply a **description of the virus's genetic makeup** and its origin in birds. - It does not explain why the virus has or has not become an epidemic in humans; rather, it indicates the source of the virus.

Q: SAFE strategy has been developed for the control of:

Trachoma. ***Trachoma*** - The **SAFE strategy** is a comprehensive public health intervention specifically designed and recommended by the WHO for the global elimination of **trachoma**. - SAFE stands for **Surgery** for trichiasis, **Antibiotics** to treat Chlamydia trachomatis infection, **Facial cleanliness** to reduce transmission, and **Environmental improvement** to prevent reinfection. *Refractive errors* - Refractive errors are corrected with eyeglasses, contact lenses, or refractive surgery, not through the **SAFE strategy**. - While vision impairment is a concern in both, the underlying pathology and interventions are entirely different. *Ocular trauma* - Ocular trauma refers to injuries to the eye and requires immediate medical or surgical intervention, depending on the severity. - Its prevention and management do not involve the **SAFE strategy**, which targets infectious disease. *Diabetic retinopathy* - Diabetic retinopathy is a complication of diabetes affecting the eyes. Management involves controlling blood sugar, blood pressure, and cholesterol, and specific ophthalmological treatments like laser photocoagulation or anti-VEGF injections. - The **SAFE strategy** is unrelated to the pathogenesis or treatment of diabetic retinopathy.

Q: Zoonoses are all except-

Guinea worm infestation. ***Guinea worm infestation*** - **Dracunculiasis (Guinea worm disease)** is exclusively a human disease (anthroponosis), meaning humans are the only definitive hosts. - The life cycle involves humans as the primary host and **copepods** (small crustaceans) as intermediate hosts; there is no animal reservoir or transmission to/from other vertebrate animals. - This is **NOT a zoonosis** because it does not involve animal-to-human transmission. *Plague* - **Plague** is a classic zoonosis caused by *Yersinia pestis*, primarily affecting rodents and transmitted to humans via **flea bites**. - Rodents (especially rats) serve as natural reservoirs, making this a clear example of animal-to-human disease transmission. *Rabies* - **Rabies** is a viral zoonotic disease transmitted to humans through the saliva of infected animals, most commonly via **bites from infected animals**. - The main reservoirs are **carnivorous mammals** such as dogs, foxes, bats, and raccoons, making it a classic zoonosis. *Hydatid cyst* - **Hydatid disease (echinococcosis)** is a zoonosis caused by the larval stage of *Echinococcus* tapeworms. - Definitive hosts are **carnivores** (e.g., dogs, wolves), and humans are accidental intermediate hosts who acquire infection through contact with infected animal feces or contaminated food/water.

Q: Rat flea transmits:

Endemic typhus. ***Endemic typhus*** - **Endemic typhus**, also known as **murine typhus**, is transmitted by the **rat flea (Xenopsylla cheopis)**, which carries the bacterium **Rickettsia typhi**. - The flea bites humans after feeding on infected rats, transmitting the bacteria. *Lassa fever* - **Lassa fever** is a **viral hemorrhagic fever** transmitted to humans primarily through contact with food or household items contaminated with urine or feces of **infected multimammate rats**. - It is not transmitted by fleas. *Trachoma* - **Trachoma** is a chronic infectious eye disease caused by the bacterium **Chlamydia trachomatis**. - It is transmitted through direct or indirect contact with eye and nose discharge of infected individuals, often via **flies (Musca sorbens)** that land on the eyes. *Rabies* - **Rabies** is a **viral disease** that is transmitted to humans through the saliva of infected animals, most commonly via a **bite** from an infected mammal such as a **dog, bat, or fox**. - It is not transmitted by fleas.

Q: Most sensitive indicator of recent transmission of malaria in a community is:-

Infant parasite rate. ***Infant parasite rate*** - This measures the proportion of infants (typically under 1 year old) in a community who have **malaria parasites** in their blood. - Since infants have limited mobility and are less likely to have been exposed to malaria in distant areas, their infection status is a direct reflection of **recent local transmission**. *Annual parasite rate* - This indicates the average number of positive malaria blood slides per 100 population per year, reflecting the **overall burden of malaria** in a community over a longer period. - While it's an important epidemiological indicator, it doesn't specifically target **recent transmission** as effectively as the infant parasite rate. *Mosquito rate* - This refers to the density or prevalence of **malaria-carrying mosquitoes** (e.g., Anopheles mosquitoes) in a given area. - While essential for understanding transmission potential, it does not directly measure human infection and therefore is not a direct indicator of **recent human transmission**. *Spleen rate* - This measures the proportion of children (typically 2-9 years old) with an **enlarged spleen**, which is a common but non-specific sign of chronic or repeated malaria infections. - It reflects past exposure and chronic malaria in the community and is not a sensitive indicator of **recent transmission**.

Q: Vertical transmission of pathogens from parent vector to offspring vector is called:

Transovarian. ***Transovarian*** - **Transovarian transmission** refers to the passage of a pathogen from an infected adult female vector directly into her offspring, often via the ova. - This mode of transmission ensures disease persistence in subsequent generations of vectors without requiring re-infection from an external host. *Mechanical transmission* - **Mechanical transmission** involves a pathogen being carried on the exterior of a vector (e.g., on legs or proboscis) from an infected host to a susceptible one, without replication or development within the vector. - The vector serves as a "flying syringe" or a simple carrier, not allowing for biological multiplication or development of the pathogen. *Cyclodevelopmental transmission* - In **cyclodevelopmental transmission**, the pathogen undergoes both developmental changes and multiplication within the vector. - An example is **filarial worms** in mosquitoes, where the parasite develops into the infective stage and also multiplies in the vector. *Propagative transmission* - **Propagative transmission** involves the pathogen multiplying within the vector but not undergoing any significant developmental changes. - A classic example is the **Arbovirus** replication within mosquitoes, where the virus replicates to high titers in the vector's tissues.

Q: Intensified malaria control under the national framework for malaria elimination is defined as:

States with API >=1. ***States with API >=1*** - Intensified malaria control under a national elimination framework targets regions with an **Annual Parasite Index (API) of 1 or greater**, indicating a significant burden of malaria requiring focused intervention. - This threshold helps prioritize resources and strategies to areas where malaria transmission is still active and potentially high, moving towards reduction and eventual elimination. *No longer a health problem* - This definition would classify an area as having achieved **malaria elimination**, which is a far more advanced stage than intensified control. - Intensified control is implemented when malaria is still a health problem, albeit one that is being actively managed to reduce its impact. *Zero incidence of malaria* - Zero incidence signifies **complete interruption of local malaria transmission**, meaning no new cases are occurring locally. - While the ultimate goal, intensified control aims to *reduce* incidence significantly, not necessarily achieve zero incidence immediately. *3 consecutive years no local transmission in the state* - This criterion typically defines **malaria elimination**, not intensified control. - Elimination is declared when there has been no local transmission for a sustained period, indicating a successful control program has halted the disease.

Q: Which of the following is the 'Yellow Fever' reference centre?

NIV, Pune. ***NIV, Pune*** - The **National Institute of Virology (NIV)** in Pune is the WHO-designated national reference laboratory for Yellow Fever in India. - It serves as a **WHO Collaborating Centre** for arboviral diseases and is responsible for Yellow Fever vaccination, diagnosis, surveillance, and outbreak investigation. - NIV Pune is the authorized center for issuing **International Certificates of Vaccination** for Yellow Fever as required under International Health Regulations. *NIN, Hyderabad* - The **National Institute of Nutrition (NIN)** in Hyderabad focuses on nutrition research, dietary guidelines, and public health nutrition. - It does not serve as a reference center for infectious diseases like Yellow Fever. *Central Institute, Kasauli* - The **Central Research Institute (CRI)** in Kasauli is primarily known as the national reference center for **rabies** and rabies vaccine production. - While it is an important biomedical research institution, it is not the designated Yellow Fever reference center in India. *Haffkine Institute, Mumbai* - The **Haffkine Institute** in Mumbai is a biomedical research institution involved in vaccine production and infectious disease research. - It is not designated as the national reference center for Yellow Fever.

Q: Which of the following is the LEAST important step in the national TB control program?

BCG vaccination. ***BCG vaccination*** - While BCG vaccination offers some protection against severe forms of TB, particularly in children, it has **limited efficacy** against adult pulmonary TB, which is the primary driver of transmission. - The national TB control program's main focus is on **interrupting transmission** by identifying and effectively treating infectious cases. *Treatment of sputum positive cases* - This is a cornerstone of TB control because **sputum-positive cases** are the primary source of airborne transmission. - Effective treatment rapidly renders patients **non-infectious**, preventing further spread of the disease within the community. *Isolation of sputum positive cases* - **Isolation** of highly infectious individuals helps to prevent the immediate spread of *Mycobacterium tuberculosis* to others in close contact. - This is a crucial **infection control measure**, especially in healthcare settings and within households. *Treatment of contacts* - Treating contacts, especially those with **latent TB infection (LTBI)** or who are at high risk of progression to active disease (e.g., immunocompromised individuals), is vital for preventing the development of new active cases. - This strategy targets the **prevention of future active disease** in individuals already exposed to the bacterium.

Q: True statement about Japanese Encephalitis is:

Pigs are amplifier hosts. ***Pigs are amplifier hosts*** - **Pigs** serve as the primary **amplifier hosts** for the Japanese Encephalitis virus, increasing the viral load in the environment and facilitating transmission to mosquitoes. - This amplification is crucial in the **epidemiology** of Japanese Encephalitis, as pigs sustain the transmission cycle between mosquitoes and maintain high viral loads. - This is the **most definitive and unique** characteristic statement about JE epidemiology. *No vaccine for JE* - This statement is incorrect; there are **effective vaccines available** for Japanese Encephalitis, recommended for travelers to endemic areas and high-risk populations. - Examples include inactivated vaccines (Ixiaro) and live-attenuated vaccines (SA 14-14-2, widely used in India's Universal Immunization Programme). *Cross reacts with Dengue virus* - While this statement is technically true, both Japanese Encephalitis virus (JEV) and Dengue virus (DENV) are **flaviviruses** and share common epitopes causing **serological cross-reactivity** in IgM/IgG tests. - However, this cross-reactivity is a **diagnostic challenge** rather than a defining epidemiological feature of JE itself. - This cross-reactivity is a property shared by multiple flaviviruses (including Zika, Yellow Fever, West Nile), making it less specific to JE. *Mortality less than 10%* - This statement is incorrect. The **case fatality rate** for symptomatic Japanese Encephalitis is significant, typically ranging from **20% to 30%**. - Even among survivors, severe neurological or psychiatric sequelae are common, affecting 30-50% of patients.

Question 1

H5N1 Avian influenza has not become an epidemic till now. What is the most important reason for this?

Accepted Answer

Human to human transmission is rare

Answer

Seen only in wild birds and not in domestic poultry

Answer

It causes serious illness leading to death of the patient

Answer

It has avian influenza genes

Question 2

SAFE strategy has been developed for the control of:

Accepted Answer

Trachoma

Answer

Refractive errors

Answer

Ocular trauma

Answer

Diabetic retinopathy

Question 3

Zoonoses are all except-

Accepted Answer

Guinea worm infestation

Answer

Plague

Answer

Rabies

Answer

Hydatid cyst

Question 4

Rat flea transmits:

Accepted Answer

Endemic typhus

Answer

Lassa fever

Answer

Trachoma

Answer

Rabies

Question 5

Most sensitive indicator of recent transmission of malaria in a community is:-

Accepted Answer

Infant parasite rate

Answer

Annual parasite rate

Answer

Mosquito rate

Answer

Spleen rate

Question 6

Vertical transmission of pathogens from parent vector to offspring vector is called:

Accepted Answer

Transovarian

Answer

Mechanical transmission

Answer

Cyclodevelopmental transmission

Answer

Propagative transmission

Question 7

Intensified malaria control under the national framework for malaria elimination is defined as:

Accepted Answer

States with API >=1

Answer

No longer a health problem

Answer

Zero incidence of malaria

Answer

3 consecutive years no local transmission in the state

Question 8

Which of the following is the 'Yellow Fever' reference centre?

Accepted Answer

NIV, Pune

Answer

NIN, Hyderabad

Answer

Central Institute, Kasauli

Answer

Haffkine Institute, Mumbai

Question 9

Which of the following is the LEAST important step in the national TB control program?

Accepted Answer

BCG vaccination

Answer

Treatment of sputum positive cases

Answer

Isolation of sputum positive cases

Answer

Treatment of contacts

Question 10

True statement about Japanese Encephalitis is:

Accepted Answer

Pigs are amplifier hosts

Answer

No vaccine for JE

Answer

Cross reacts with Dengue virus

Answer

Mortality less than 10%.

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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