Infectious Diseases Practice Questions

Q: Which one of the following mosquitoes is responsible for transmitting Japanese encephalitis?

Culex tritaeniorhynchus. ***Culex tritaeniorhynchus*** - This mosquito species is the **primary vector** for **Japanese encephalitis virus (JEV)** transmission in many endemic regions of Asia. - It typically breeds in **rice paddies** and other agricultural water sources, allowing for efficient transmission within populations. *Aedes aegypti* - This mosquito is the main vector for **Dengue**, **Chikungunya**, and **Zika** viruses. - It is not a significant vector for Japanese encephalitis. *Anopheles stephensi* - This mosquito is a major vector for **malaria**, particularly in urban areas of India. - It primarily transmits **Plasmodium parasites** and is not associated with Japanese encephalitis. *Mansonia* - Mosquitoes of the *Mansonia* genus are known vectors for **lymphatic filariasis** and some arboviruses. - They are not considered primary vectors for Japanese encephalitis.

Q: Which of the following diseases has man as an incidental host with ‘Pig → Mosquito → Pig’ as the basic cycle of transmission?

Japanese encephalitis. ***Japanese encephalitis*** - **Japanese encephalitis** is a viral disease where humans are incidental dead-end hosts. - The established transmission cycle involves **pigs as amplifying hosts** and mosquitoes (primarily *Culex tritaeniorhynchus*) as vectors, which then infect other pigs, maintaining the "Pig → Mosquito → Pig" cycle. - Water birds serve as natural reservoir hosts, while pigs amplify the virus. *Handigodu syndrome* - **Handigodu disease** is another name for **Kyasanur Forest Disease (KFD)** or a related viral hemorrhagic fever from the same region in Karnataka, India. - It is a tick-borne viral disease, not mosquito-borne, with monkeys and small mammals as reservoir hosts. - There is no "Pig → Mosquito → Pig" transmission cycle involved. *Chikungunya* - **Chikungunya** is a viral disease transmitted primarily by *Aedes aegypti* and *Aedes albopictus* mosquitoes, with humans being the primary reservoir hosts. - The transmission cycle is "Human → Mosquito → Human," not involving pigs as amplifying hosts. *Kyasanur forest disease* - **Kyasanur forest disease (KFD)** is a viral hemorrhagic fever transmitted by *Haemaphysalis* ticks, with monkeys and small mammals serving as reservoir hosts. - The transmission cycle involves ticks and forest animals, not pigs and mosquitoes, and humans are incidental hosts.

Q: What is the most important test to assess the prevalence of tuberculosis infection in a community?

Tuberculin test. ***Tuberculin test*** - The **tuberculin skin test (TST)**, or Mantoux test, measures the delayed-type hypersensitivity reaction to tuberculin, indicating prior exposure to *Mycobacterium tuberculosis*. - A positive TST reflects **tuberculosis infection**, whether latent or active, making it a valuable tool for assessing prevalence in a community. *Mass miniature radiography* - This method, now largely replaced by digital radiography, primarily detects **active pulmonary tuberculosis** by identifying lung lesions like infiltrates or cavities. - It is less effective for detecting **latent tuberculosis infection (LTBI)**, which represents the majority of infected individuals in a community. *Sputum examination of AFB* - This test is crucial for diagnosing **active pulmonary tuberculosis** by identifying acid-fast bacilli (AFB) in sputum. - However, it only detects individuals who are actively shedding bacteria and may not capture the broader prevalence of **latent infection** in a community. *Clinical examination* - A clinical examination primarily identifies individuals with **symptoms of active tuberculosis**, such as persistent cough, fever, or weight loss. - It is not a reliable method for assessing the overall **prevalence of tuberculosis infection**, particularly asymptomatic latent cases, in a community.

Q: What is the window period for HIV infection?

6 – 24 weeks. ***6 – 24 weeks*** - The **window period** for HIV infection refers to the time after initial infection during which **antibodies have not yet developed** to a detectable level. - While it can vary depending on the testing method, the **6-24 week range** generally encompasses the period for traditional antibody tests to become positive. - This is the **conservative estimate** used for conventional HIV antibody testing, ensuring adequate time for seroconversion in most individuals. *3 – 6 weeks* - While many individuals will develop detectable antibodies within this timeframe, this range is **too narrow** to capture all cases of seroconversion. - Some individuals may take longer (up to 12 weeks or more) to develop detectable antibody levels, making this an **incomplete window period**. - The 6-24 week range provides a more **conservative and comprehensive** testing window. *3 – 15 days* - This timeframe is typically **too short** for the body to produce a detectable antibody response to HIV. - **Early HIV infection** during this period would likely be detected by more sensitive tests, such as **HIV RNA PCR**, which detect viral genetic material directly. - This represents the **eclipse period** rather than the full antibody window period. *6 – 8 months* - While some individuals may take longer to seroconvert, 6-8 months is generally considered **outside the typical window period** for most conventional HIV antibody tests. - Most people will develop detectable antibodies much earlier than this, usually within **3-12 weeks**. - This timeframe is excessively long and not reflective of standard testing protocols.

Q: With reference to dengue virus, consider the following statements: 1. In India, all the four serotypes are found. 2. The reservoir of infection is both man and mosquito. 3. Adults usually have a milder disease than children. 4. Dengue hemorrhagic fever is caused by infection with more than one dengue virus. Which of the statements given above is/are correct?

1, 2 and 4. ***1, 2 and 4*** - **All four serotypes** (DEN-1, DEN-2, DEN-3, and DEN-4) of the dengue virus are endemic in India, contributing to the recurrent outbreaks seen across the country. - Dengue is a **vector-borne disease**, meaning the virus cycles between humans (the primary reservoir) and mosquitoes (specifically *Aedes aegypti* and *Aedes albopictus*), making both essential for its transmission. - **Dengue hemorrhagic fever (DHF)**, or severe dengue, is often associated with a **second infection by a different serotype** of the dengue virus due to antibody-dependent enhancement (ADE). *2, 3 and 4* - The statement that adults usually have a milder disease than children is **incorrect**; children often present with milder, non-specific symptoms, while adults are more likely to develop typical dengue fever or severe forms. - The other statements regarding the presence of all four serotypes, the reservoir, and the cause of DHF are correct. *4 only* - While statement 4 (DHF caused by infection with more than one serotype) is correct, it overlooks the accuracy of statements 1 and 2. - Omitting statements 1 and 2 makes this option incomplete as both are established facts about dengue. *1 and 2 only* - This option correctly identifies that all four serotypes exist in India and that humans and mosquitoes serve as reservoirs. - However, it **incorrectly excludes statement 4** regarding the etiology of dengue hemorrhagic fever (DHF), which results from sequential infection with a different serotype.

Q: Consider the following vectors: 1. Aedes mosquito 2. Flea 3. Ticks 4. Itchmite Transovarian transmission is demonstrated in

1 and 3. ***1 and 3*** - **Aedes mosquito** (*Aedes aegypti*, *Aedes albopictus*) demonstrates well-established transovarian transmission for multiple arboviruses including **dengue**, **Zika**, **chikungunya**, and **yellow fever**. This mechanism allows the virus to persist in mosquito populations even without vertebrate hosts. - **Ticks** (e.g., *Ixodes*, *Dermacentor*, *Amblyomma* species) are classic examples of transovarian transmission, transmitting pathogens like **Rickettsia** (Rocky Mountain spotted fever, tick typhus), **Babesia**, **Crimean-Congo hemorrhagic fever virus**, and **Kyasanur Forest disease virus**. This is a key epidemiological feature distinguishing tick-borne diseases. *2 and 4* - **Fleas** primarily transmit **plague** (*Yersinia pestis*) horizontally through infected flea bites or contaminated feces. While some rickettsiae (*R. typhi*, *R. felis*) can show limited transovarian transmission in fleas, this is not a prominent or classically emphasized feature compared to mosquitoes and ticks. - **Itchmite** (*Sarcoptes scabiei*) causes **scabies** by direct skin infestation and is not a vector for other pathogens. It does not demonstrate transovarian transmission of disease agents. *1 and 2* - While **Aedes mosquitoes** demonstrate prominent transovarian transmission, **fleas** do not typically exhibit this as a major transmission mode for their primary pathogens. *3 and 4* - **Ticks** exhibit transovarian transmission, but **itchmite** is a direct parasite, not a disease vector with transovarian transmission capability.

Q: Consider the following statements: Prophylactic disinfection includes 1. disinfection of urine specimen of patient with enteric fever 2. pasteurization of milk 3. disinfection of contaminated linen 4. disinfection of water by chlorine Which of these statements are correct?

2 and 4 only. ***Correct: 2 and 4 only*** - **Prophylactic (preventive) disinfection** is performed on materials that are *potentially* contaminated to prevent disease transmission BEFORE actual contamination occurs - **Pasteurization of milk** and **chlorination of water** are classic examples of prophylactic measures applied to substances before consumption - These are routine public health interventions performed regardless of known contamination *Incorrect: 1 and 3 only* - This incorrectly classifies **disinfection of urine specimens from enteric fever patients** and **disinfection of contaminated linen** as prophylactic measures - Both are examples of **concurrent/terminal disinfection** (performed on materials already known to be contaminated from infected patients) - Misses pasteurization and chlorination which are true prophylactic measures *Incorrect: 1, 2, 3 and 4* - While statements 2 and 4 are correct examples of prophylactic disinfection, statements 1 and 3 are NOT - **Statement 1** (disinfection of urine from enteric fever patient) is **concurrent disinfection** - the patient is already infected, and we're disinfecting their excreta - **Statement 3** (disinfection of contaminated linen) is **concurrent/terminal disinfection** - the linen is already contaminated - Prophylactic measures are preventive; concurrent/terminal measures deal with known contamination *Incorrect: 1, 2 and 4 only* - Incorrectly includes statement 1 (disinfection of urine from infected patient) which is concurrent disinfection, not prophylactic - Also incorrectly excludes statement 3 while the issue is that both 1 and 3 are not prophylactic measures

Q: Consider the following diseases: 1. Rift valley fever 2. Yellow Fever 3. Chikungunya fever 4. West Nile fever Which of the above diseases are transmitted by Aedes mosquito?

1, 2 and 3. ***1, 2 and 3*** - **Rift Valley fever**, **Yellow fever**, and **Chikungunya fever** are all primarily transmitted to humans through the bites of infected **Aedes mosquitoes**. - The **Aedes aegypti** and **Aedes albopictus** species are particularly significant vectors for these viral diseases. *1, 2 and 4* - This option incorrectly includes **West Nile fever** while omitting **Chikungunya fever**. - **West Nile fever** is primarily transmitted by **Culex mosquitoes**, not Aedes mosquitoes. *2, 3 and 4* - This option incorrectly includes **West Nile fever** as an Aedes mosquito-borne disease. - **Yellow fever** and **Chikungunya fever** are indeed transmitted by Aedes mosquitoes, but **West Nile fever** is not. *1, 3 and 4* - This option incorrectly includes **West Nile fever** in the list of Aedes-borne diseases. - While **Rift Valley fever** and **Chikungunya fever** are transmitted by Aedes mosquitoes, **West Nile fever** is primarily transmitted by Culex species.

Question 1

As per ICMR guidelines, which of the following are the criteria for SARS-COV-2 exposure for a pregnant female during the COVID-19 pandemic?

1. Travel to an affected country within previous 14 days
2. Close contact with a confirmed case within a distance of 1 metre for more than 15 minutes
3. Residing in a containment zone
4. Healthcare workers examining a confirmed case without adequate protection

Accepted Answer

1, 2 and 4

Answer

1, 2 and 3

Answer

1, 3 and 4

Answer

2, 3 and 4

Question 2

Which one of the following mosquitoes is responsible for transmitting Japanese encephalitis?

Accepted Answer

Culex tritaeniorhynchus

Answer

Aedes aegypti

Answer

Anopheles stephensi

Answer

Mansonia

Question 3

Which of the following diseases has man as an incidental host with ‘Pig → Mosquito → Pig’ as the basic cycle of transmission?

Accepted Answer

Japanese encephalitis

Answer

Handigodu syndrome

Answer

Chikungunya

Answer

Kyasanur forest disease

Question 4

What is the most important test to assess the prevalence of tuberculosis infection in a community?

Accepted Answer

Tuberculin test

Answer

Mass miniature radiography

Answer

Sputum examination of AFB

Answer

Clinical examination

Question 5

What is the window period for HIV infection?

Accepted Answer

6 – 24 weeks

Answer

3 – 6 weeks

Answer

3 – 15 days

Answer

6 – 8 months

Question 6

With reference to dengue virus, consider the following statements:

1. In India, all the four serotypes are found.
2. The reservoir of infection is both man and mosquito.
3. Adults usually have a milder disease than children.
4. Dengue hemorrhagic fever is caused by infection with more than one dengue virus. Which of the statements given above is/are correct?

Accepted Answer

1, 2 and 4

Answer

2, 3 and 4

Answer

4 only

Answer

1 and 2 only

Question 7

Consider the following features of food poisoning:
'Incubation period less than 24 hours, source of infection is milk products, and symptoms include diarrhoea and vomiting.'
To which of the following does the above description apply?

1. Staphylococcal food poisoning
2. Salmonella food poisoning
3. Botulism
Select the correct answer using the code given below:

Accepted Answer

1 only

Answer

2 only

Answer

1 and 3

Answer

1 and 2

Question 8

Consider the following vectors:

1. Aedes mosquito
2. Flea
3. Ticks
4. Itchmite

Transovarian transmission is demonstrated in

Accepted Answer

1 and 3

Answer

2 and 4

Answer

1 and 2

Answer

3 and 4

Question 9

Consider the following statements: Prophylactic disinfection includes

1. disinfection of urine specimen of patient with enteric fever 
2. pasteurization of milk 
3. disinfection of contaminated linen 
4. disinfection of water by chlorine Which of these statements are correct?

Accepted Answer

2 and 4 only

Answer

1 and 3 only

Answer

1, 2, 3 and 4

Answer

1, 2 and 4 only

Question 10

Consider the following diseases:

1. Rift valley fever

2. Yellow Fever

3. Chikungunya fever

4. West Nile fever

Which of the above diseases are transmitted by Aedes mosquito?

Accepted Answer

1, 2 and 3

Answer

1, 2 and 4

Answer

2, 3 and 4

Answer

1, 3 and 4

Infectious Diseases — MCQs

Infectious Diseases — MCQs

On this page

Practice by Chapter

Want unlimited practice?