Infectious Diseases Practice Questions

Q: All are true regarding Japanese encephalitis except which of the following?

Horses are amplifier hosts. ***Horses are amplifier hosts*** - **Horses** can act as **sentinel animals** and develop severe neurological disease, but they are generally considered **dead-end hosts** for Japanese encephalitis virus, meaning they do not amplify the virus to a level sufficient to transmit it further. - The primary **amplifier hosts** for Japanese encephalitis are **pigs and wading birds**, which maintain the transmission cycle. *Caused by flavivirus* - Japanese encephalitis is indeed caused by a **flavivirus**, specifically the **Japanese encephalitis virus (JEV)**, which belongs to the Flaviviridae family. - This characteristic is consistent with the general epidemiology and pathogenesis of other well-known flaviviruses like Dengue and West Nile virus. *Humans are dead-end hosts* - **Humans** are considered **dead-end hosts** for Japanese encephalitis because the **viremia** (virus levels in the blood) in infected humans is typically too low to infect mosquitoes that feed on them. - This means that humans do not contribute to the ongoing transmission cycle of the virus between mosquitoes and amplifier hosts. *Transmitted by culex* - The primary vectors for Japanese encephalitis virus are mosquitoes of the **Culex genus**, particularly **Culex tritaeniorhynchus**. - These mosquitoes typically breed in rice paddies and other agricultural wetlands, which are common in regions where the disease is endemic.

Q: Identify the disease represented in the image.

Japanese encephalitis. ***Japanese encephalitis*** - The image likely depicts a mosquito vector, specifically from the *Culex* genus, which is the primary vector for **Japanese encephalitis virus**. - Common vectors of Japanese encephalitis are **Culex tritaeniorhynchus** and **Culex vishnui**. *Dengue* - Dengue virus is primarily transmitted by mosquitoes from the *Aedes* genus, especially **Aedes aegypti** and **Aedes albopictus**. - These mosquitoes are characterized by **distinctive white bands** on their legs and bodies. *Chikungunya* - Chikungunya is also transmitted by *Aedes* mosquitoes, mainly **Aedes aegypti** and **Aedes albopictus**. - The distinguishing feature of these vectors is not evident in the context of the question's focus on the depicted image. *Zika virus* - Zika virus is primarily transmitted by **Aedes aegypti**, the same mosquito responsible for dengue and chikungunya. - The image does not provide enough specific morphological details to differentiate it from other *Aedes*-borne diseases without additional context.

Q: Range of flight of Aedes mosquito is?

400 m. ***400 m*** - *Aedes* mosquitoes have a **typical flight range of up to 400 meters** from their breeding sites, which is well-established in vector control literature. - This flight range is a critical factor in planning **control measures and source reduction strategies**, as interventions need to cover a 400m radius around cases. - Most *Aedes aegypti* prefer to stay within **50-100 meters** but can disperse up to 400m when searching for blood meals or oviposition sites. *Less than 100 m* - While many *Aedes* mosquitoes do stay within **100 meters** of their breeding sites under normal conditions, this represents their **preferred range** rather than maximum capability. - The **maximum flight range** extends beyond this distance, making this answer too restrictive for vector control planning. *1 km* - A flight range of **1 km** exceeds the typical dispersal distance for *Aedes* mosquitoes under normal circumstances. - While occasional long-distance dispersal has been documented, this is not the standard flight range used in epidemiological planning. *10 km* - This distance is far too great for *Aedes* mosquitoes, which are relatively weak fliers. - Such long distances would require **passive transport** (vehicles, wind) rather than active flight.

Q: Major reservoir of KFD?

Squirrels. ***Squirrels*** - **Squirrels** are considered a major reservoir for the Kyasanur Forest Disease (KFD) virus because they can carry the virus without showing severe symptoms themselves, allowing for viral persistence in nature. - The virus can be transmitted from infected squirrels to ticks, which then can spread the infection to other animals or humans. *Human* - Humans are considered **incidental hosts** for KFD, meaning they can become infected but do not typically play a significant role in maintaining the virus in nature. - While humans can experience severe disease, they do not serve as a reservoir for further transmission to other vectors or hosts. *Cattle* - **Cattle** are not typically considered a reservoir for the Kyasanur Forest Disease virus. - They can be exposed to KFD but are not known to sustain the viral cycle or transmit it effectively to ticks or other animals. *Monkey* - While KFD is often associated with **monkey deaths** (especially black-faced langurs and bonnet macaques), these animals are considered **amplifying hosts** rather than primary reservoirs. - Monkeys experience severe disease and high mortality, making them good indicators of viral activity but not long-term carriers for sustained transmission.

Q: What is the recommended mesh size for mosquito nets to effectively prevent mosquito bites?

156 holes per square inch. ***156 holes per square inch*** - This mesh size, equivalent to a **hole dimension of 1.5mm x 1.5mm**, is recommended by the **WHO** for insecticide-treated nets (ITNs) to effectively prevent mosquito entry. - It provides a balance between sufficient air circulation and preventing even smaller mosquito species from passing through. *50 holes per square inch* - This mesh size is too large and would allow **smaller mosquito species** to easily pass through, rendering the net ineffective. - It would not provide adequate **protection** against mosquito bites and disease transmission. *100 holes per square inch* - While better than 50 holes, this mesh size might still be insufficient to block all mosquito species, especially very small ones. - It does not meet the **WHO guidelines** for optimal protection. *200 holes per square inch* - Although this size would effectively block mosquitoes, it might excessively restrict **airflow**, making the net uncomfortable to sleep under in warm climates. - Higher mesh counts can also lead to **increased production costs** and potential issues with durability.

Q: Best indicator for spread of TB in a community?

Annual infection rate. ***Annual infection rate*** - The **Annual Infection Rate (ARI)** is the gold standard indicator for measuring TB spread in a community - It measures the rate at which new TB infections occur in a tuberculin-negative population over one year - ARI directly reflects **recent transmission** and the force of infection in the community - WHO and Park's Textbook recommend ARI as the best epidemiological indicator for TB transmission - Calculated through tuberculin surveys showing conversion from negative to positive - An ARI of 1% indicates 1% of uninfected individuals become infected per year *Incidence of new cases* - Incidence measures new **disease cases** (active TB), not new infections - Only 5-10% of TB infections progress to active disease, often after years of latency - Incidence is affected by case detection rates, diagnostic capacity, and healthcare access - It underestimates actual transmission occurring in the community *Prevalence of infection* - **Prevalence** indicates total existing cases (both old and new) at a point in time - Influenced by both new infections and duration of infection/disease - Does not specifically measure the rate of ongoing transmission *Case rate* - **Case rate** refers to the number of active disease cases per population - Similar to prevalence, it doesn't isolate new transmission events - Less sensitive for detecting changes in transmission dynamics

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

Syndromic. ***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.

Q: What was the color of the box containing drugs for the treatment of Category I tuberculosis (TB) under the DOTS program?

Yellow. ***Yellow*** - The **yellow box** was designated for **Category I TB drugs** under the **DOTS (Directly Observed Treatment, Short-course)** strategy. - Category I treated **newly diagnosed sputum smear-positive pulmonary TB**, severely ill smear-negative cases, and severe extrapulmonary TB. - **Note:** India transitioned from category-based to **weight-based TB treatment** in 2012 under NTEP (formerly RNTCP). This color-coded system is now historical. *Red* - The **red box** was used for **Category II TB treatment**, covering **retreatment cases** (relapse, treatment failure, or treatment after default). - These regimens included additional drugs like streptomycin with different durations compared to Category I. *Blue* - The **blue box** was used for **Category III TB treatment** in the DOTS program. - Category III covered new smear-negative pulmonary TB cases and less severe extrapulmonary TB. *Green* - The **green box** was not part of the standard category-based DOTS framework for TB drug distribution. - The three main categories used yellow, red, and blue color-coding to prevent dispensing errors.

Q: Varicella zoster virus infection is more likely to occur in which of the following months?

March. ***March*** - Varicella-zoster virus (VZV) infections, particularly **chickenpox**, show a peak incidence during **late winter and spring months**. - This seasonality is attributed to changes in human behavior and environmental factors that facilitate transmission. *August* - **August** is typically a summer month in many regions, and VZV infections are less common during warmer periods. - Reduced indoor crowding and increased exposure to UV light may contribute to lower transmission rates. *October* - While October marks the beginning of autumn, it generally precedes the peak season for VZV infections. - Transmission rates start to increase but are usually not as high as in late winter or early spring. *November* - November, late autumn or early winter, sees an increase in respiratory and viral infections due to colder weather and increased indoor gatherings. - However, the peak incidence for VZV is typically observed a few months later, in late winter and early spring.

Question 1

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?

Accepted Answer

Condom distribution and needle exchange programs

Answer

Public awareness campaigns and abstinence education

Answer

Antiretroviral therapy and nutritional support

Answer

Routine screening and treatment of STIs

Question 2

All are true regarding Japanese encephalitis except which of the following?

Accepted Answer

Horses are amplifier hosts

Answer

Humans are dead-end hosts

Answer

Caused by flavivirus

Answer

Transmitted by culex

Question 3

Identify the disease represented in the image.

Accepted Answer

Japanese encephalitis

Answer

Dengue

Answer

Chikungunya

Answer

Zika virus

Question 4

Range of flight of Aedes mosquito is?

Accepted Answer

400 m

Answer

1 km

Answer

Less than 100 m

Answer

10 km

Question 5

Major reservoir of KFD?

Accepted Answer

Squirrels

Answer

Human

Answer

Cattle

Answer

Monkey

Question 6

What is the recommended mesh size for mosquito nets to effectively prevent mosquito bites?

Accepted Answer

156 holes per square inch

Answer

50 holes per square inch

Answer

100 holes per square inch

Answer

200 holes per square inch

Question 7

Best indicator for spread of TB in a community?

Accepted Answer

Annual infection rate

Answer

Prevalence of infection

Answer

Incidence of new cases

Answer

Case rate

Question 8

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

Accepted Answer

Syndromic

Answer

Preventive

Answer

Symptomatic

Answer

Rehabilitative

Question 9

What was the color of the box containing drugs for the treatment of Category I tuberculosis (TB) under the DOTS program?

Accepted Answer

Yellow

Answer

Blue

Answer

Green

Answer

Red

Question 10

Varicella zoster virus infection is more likely to occur in which of the following months?

Accepted Answer

March

Answer

August

Answer

October

Answer

November

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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