Infectious Diseases Practice Questions

Q: Which of the following diseases does not have healthy carriers?

Measles. ***Measles*** - Measles is a highly contagious viral disease that typically presents with a characteristic **rash**, **fever**, **cough**, **coryza**, and **conjunctivitis**. - Individuals infected with measles are usually symptomatic and contagious during the **prodromal phase** and until several days after the rash appears; asymptomatic carriage is generally not observed. *Diphtheria* - Healthy carriers of **Corynebacterium diphtheriae** can exist, particularly in the pharynx or skin, without showing overt disease symptoms. - These carriers can still **transmit the bacteria** to susceptible individuals, making them a public health concern. *Salmonellosis* - Individuals infected with **Salmonella Typhi** (which causes typhoid fever) can become asymptomatic chronic carriers, shedding bacteria in their stool for years. - While other Salmonella species can cause acute gastroenteritis, chronic asymptomatic carriage is most notable with **typhoid fever**. *Poliomyelitis* - Many individuals infected with the **poliovirus** can be asymptomatic and shed the virus in their stool. - These healthy carriers play a significant role in the **transmission of the virus** within communities, making eradication challenging.

Q: According to DOTS-PLUS guidelines 2013, which of the following statements about the treatment of multidrug-resistant TB is incorrect?

Continuation phase - 2 drugs. ***Continuation phase - 2 drugs*** - According to DOTS-PLUS guidelines (2013), the continuation phase for multidrug-resistant TB (MDR-TB) should include at least **three to four effective drugs**, not two. - Using only two drugs in the continuation phase would be grossly inadequate and would likely lead to treatment failure and the development of extensively drug-resistant TB (XDR-TB). - This statement is **clearly incorrect** and represents a major deviation from standard treatment protocols. *Total duration 24-27 months* - According to DOTS-PLUS 2013 guidelines, the total treatment duration for MDR-TB is typically **18-24 months** (at least 18 months after culture conversion). - In complex cases, treatment may be extended beyond 24 months, though 24-27 months falls within acceptable parameters for difficult cases. - This statement is essentially correct for the upper range of treatment duration. *Intensive phase 6-9 months* - The intensive phase for MDR-TB treatment is indeed typically **6-9 months** or until culture conversion is documented. - This phase includes daily injectable agents and multiple oral drugs to rapidly reduce bacterial load. - This statement is **correct**. *Intensive phase - 6 drugs* - The 2013 DOTS-PLUS guidelines recommend an intensive phase regimen comprising **at least 4 effective drugs including an injectable agent**. - A 5-6 drug regimen may be used in complex cases or when drug susceptibility is uncertain. - While not the minimum standard, using 6 drugs is within acceptable practice, making this statement **generally correct**.

Q: How do hookworms infect humans?

Contaminated soil. ***Contaminated soil*** - Hookworm larvae (filariform larvae) present in **contaminated soil** can penetrate unbroken human skin, typically through the feet. - This penetration is the primary mode of infection for humans in endemic areas. *Water* - While some parasitic protozoa are transmitted through contaminated water, hookworms primarily infect via **skin penetration** from soil. - Ingestion of contaminated water is not a common or direct route for hookworm infection. *Food* - Hookworm infection is generally not acquired through the ingestion of **contaminated food**. - Infections spread via food usually involve other parasitic organisms like *Taenia* species or *Ascaris lumbricoides* eggs. *Human feces* - Human feces contain hookworm eggs, which hatch into rhabditiform larvae and then mature into infectious filariform larvae in the soil. - However, direct contact with **feces** itself is not the immediate infective route; the larvae in the soil are the infective stage.

Q: Which of the following diseases is primarily transmitted by soft ticks?

Relapsing fever. ***Relapsing fever*** - **Relapsing fever** is primarily caused by **spirochete bacteria** (Borrelia species) transmitted by **soft ticks** (Ornithodoros species). - The disease is characterized by recurrent episodes of **fever** separated by afebrile periods. *Hemorrhagic fever* - **Hemorrhagic fevers** are caused by various viruses (e.g., Ebola, Marburg, Dengue, Lassa) and are typically transmitted by **mosquitoes**, **rodents**, or direct contact, not primarily soft ticks. - While some tick-borne diseases can cause hemorrhagic symptoms, the term "hemorrhagic fever" is not specific to soft tick transmission. *Tick typhus* - **Tick typhus** (Rocky Mountain spotted fever, etc.) is caused by **Rickettsia bacteria** and is transmitted by **hard ticks** (Ixodidae family), not soft ticks. - Symptoms include fever, rash, and headache. *Tularemia* - **Tularemia** is caused by the bacterium **Francisella tularensis** and can be transmitted by various means including **hard ticks**, deer flies, direct contact with infected animals, or inhalation. - While ticks can transmit tularemia, it is not primarily associated with **soft ticks** in the same way relapsing fever is.

Q: Disease caused by a virus of the family of RNA paramyxovirus, with an incubation period of 14-21 days, high secondary attack rate, and the most common complication being aseptic meningitis. A live, attenuated vaccine is available for the disease, with the Jeryl Lynn strain. What is the name of this disease?

Mumps. ***Mumps*** - Mumps is caused by an **RNA paramyxovirus** and has a typical incubation period of **14-21 days**. - It is known for its **high secondary attack rate** and **aseptic meningitis** as the most common complication, aligning perfectly with the provided description. - The vaccine is developed from the **Jeryl Lynn strain**, which is the hallmark identifying feature of mumps vaccine. *Measles* - While also caused by an **RNA paramyxovirus** with a high attack rate, measles is primarily characterized by a **maculopapular rash** and respiratory symptoms, not aseptic meningitis as its most common complication. - The incubation period for measles is typically shorter, around **7-14 days**, and the vaccine strain is usually **Edmonston-Zagreb or Schwarz**, not Jeryl Lynn. *Rubella* - Rubella is caused by an **RNA togavirus**, not a paramyxovirus, and is characterized by a milder rash and lymphadenopathy. - The incubation period is typically **12-23 days**, but the viral family and common complications do not match the description. - Complications such as arthritis or encephalitis are rare. *Chicken pox* - Chickenpox is caused by the **varicella-zoster virus**, which is a **DNA herpesvirus**, not an RNA paramyxovirus. - It is characterized by a **vesicular rash** and can lead to complications like pneumonia or encephalitis, but not aseptic meningitis as its most common complication.

Q: Walter Reed is associated with which disease?

Yellow Fever. ***Yellow Fever*** - **Walter Reed** led the US Army Yellow Fever Commission in **Cuba** in 1900. - His team definitively proved that **Aedes aegypti mosquitoes** transmit **yellow fever**. *Typhoid Fever* - While significant medical advancements were made in understanding **typhoid fever** around the same time, Walter Reed's primary focus was not on this disease. - The mode of transmission for typhoid (contaminated food and water) was established by others, notably **Robert Koch** and **George Soper**. *Plague* - **Plague**, caused by the bacterium **Yersinia pestis**, is primarily transmitted by fleas from rodents to humans. - Walter Reed's research did not involve **plague**. *Malaria* - **Malaria** is transmitted by **Anopheles mosquitoes**, and its causative agent, **Plasmodium**, was identified by **Alphonse Laveran**. - Although also a mosquito-borne illness, Walter Reed's specific groundbreaking work was on **yellow fever**.

Q: Transovarian transmission is seen in which infection?

Rocky Mountain spotted fever. ***Rocky Mountain spotted fever*** - Transovarian transmission is a key characteristic of the **Rickettsia rickettsii** bacteria, the causative agent of Rocky Mountain spotted fever. - This mechanism ensures that the pathogen is passed from an infected female tick to her offspring, thereby maintaining the infection in the **tick population**. *Plague* - Plague (caused by **Yersinia pestis**) is primarily transmitted to humans through the bite of infected **fleas** or contact with infected animals. - It does not demonstrate transovarian transmission within its vector (fleas) as a common mode of perpetuation. *Filarial* - Filarial infections are caused by **nematodes** and are transmitted by insect vectors like mosquitoes or blackflies. - While these vectors transmit the larvae, they do not typically pass the parasitic infection to their offspring via transovarian transmission. *Guinea* - Guinea worm disease (**Dracunculus medinensis**) is transmitted when people drink water contaminated with copepods (water fleas) infected with **Guinea worm larvae**. - There is no transovarian transmission involved in the life cycle of the Guinea worm or its intermediate host.

Q: Which of the following diseases is MOST characteristically associated with Aedes aegypti transmission globally?

Dengue fever. ***Dengue fever*** - *Aedes aegypti* is the **primary vector** for dengue fever globally, making it the most characteristic association. - This mosquito species is prevalent in tropical and subtropical regions where dengue is endemic. *Japanese encephalitis* - Japanese encephalitis is primarily transmitted by **Culex mosquitoes**, particularly *Culex tritaeniorhynchus*, not *Aedes aegypti*. - It is prevalent in Asia and typically associated with rural agricultural areas. *Yellow fever* - While *Aedes aegypti* can transmit yellow fever, it is not the **most characteristic association globally** as other *Aedes* species and *Haemagogus* species are also significant vectors, especially in sylvatic cycles. - Yellow fever's geographical distribution is more restricted to parts of Africa and South America. *Chikungunya* - Chikungunya is transmitted by both **Aedes aegypti** and **Aedes albopictus**. - While *Aedes aegypti* is a vector, *Aedes albopictus* has also played a significant role in recent outbreaks, and its characteristic association is with both species rather than exclusively *Aedes aegypti*.

Q: A cook prepares sandwiches for 10 people going for a picnic. Eight out of them develop severe gastroenteritis within 4-6 hours of consuming the sandwiches. It is likely that on investigation, the cook is found to be the carrier of -

Staphylococcus aureus. ***Staphylococcus aureus*** - The rapid onset of symptoms (4-6 hours) and the development of severe gastroenteritis in multiple individuals after consuming common food items (sandwiches) strongly suggest a **preformed toxin ingestion**. - **_Staphylococcus aureus_** is a common cause of food poisoning due to its ability to produce enterotoxins that are heat-stable and cause rapid onset of nausea, vomiting, and diarrhea. *Salmonella typhi* - **_Salmonella typhi_** causes typhoid fever, which typically has an incubation period of **1-3 weeks**, much longer than the 4-6 hours seen in this case. - The symptoms of typhoid fever are also more systemic, including high fever, headache, and abdominal pain, rather than acute gastroenteritis with rapid onset. *Vibrio cholerae* - **_Vibrio cholerae_** causes cholera, characterized by **profuse watery diarrhea** with a typical incubation period of **1-5 days**. - The rapid onset of symptoms in this scenario (4-6 hours) does not align with the incubation period of cholera. *Entamoeba histolytica* - **_Entamoeba histolytica_** causes amoebiasis, which has an incubation period ranging from **several days to weeks or even months**. - It typically presents with **bloody diarrhea** and abdominal pain, and its slow onset is inconsistent with the acute event described.

Q: Which disease is primarily associated with soil as both a source and a reservoir for infection?

Tetanus. ***Correct: Tetanus*** - The causative agent, *Clostridium tetani*, forms **spores** that are widespread in **soil** and animal feces. - Soil acts as both a **source** for the bacteria to enter wounds and a **reservoir** where it can persist for long periods. - Spores are highly resistant and can survive in soil for years. *Incorrect: Rabies* - Primarily transmitted through the **saliva of infected animals**, usually via bites. - Animals (dogs, bats, etc.), not soil, serve as the primary **reservoir** for the rabies virus. *Incorrect: Typhoid* - Caused by *Salmonella Typhi*, which is transmitted through **contaminated food and water** via fecal-oral routes. - **Humans are the only known reservoir** for *Salmonella Typhi*, with chronic carriers shedding the bacteria in their feces. *Incorrect: Measles* - A highly contagious viral disease spread through **respiratory droplets** from an infected person. - **Humans are the only natural reservoir** for the measles virus.

Question 1

Which of the following diseases does not have healthy carriers?

Accepted Answer

Measles

Answer

Diphtheria

Answer

Salmonellosis

Answer

Poliomyelitis

Question 2

According to DOTS-PLUS guidelines 2013, which of the following statements about the treatment of multidrug-resistant TB is incorrect?

Accepted Answer

Continuation phase - 2 drugs

Answer

Total duration 24-27 months

Answer

Intensive phase 6-9 months

Answer

Intensive phase - 6 drugs

Question 3

How do hookworms infect humans?

Accepted Answer

Contaminated soil

Answer

Water

Answer

Food

Answer

Human feces

Question 4

Which of the following diseases is primarily transmitted by soft ticks?

Accepted Answer

Relapsing fever

Answer

Tick typhus

Answer

Hemorrhagic fever

Answer

Tularemia

Question 5

Disease caused by a virus of the family of RNA paramyxovirus, with an incubation period of 14-21 days, high secondary attack rate, and the most common complication being aseptic meningitis. A live, attenuated vaccine is available for the disease, with the Jeryl Lynn strain. What is the name of this disease?

Accepted Answer

Mumps

Answer

Measles

Answer

Rubella

Answer

Chicken pox

Question 6

Walter Reed is associated with which disease?

Accepted Answer

Yellow Fever

Answer

Typhoid Fever

Answer

Plague

Answer

Malaria

Question 7

Transovarian transmission is seen in which infection?

Accepted Answer

Rocky Mountain spotted fever

Answer

Plague

Answer

Filarial

Answer

Guinea

Question 8

Which of the following diseases is MOST characteristically associated with Aedes aegypti transmission globally?

Accepted Answer

Dengue fever

Answer

Japanese encephalitis

Answer

Chikungunya

Answer

Yellow fever

Question 9

A cook prepares sandwiches for 10 people going for a picnic. Eight out of them develop severe gastroenteritis within 4-6 hours of consuming the sandwiches. It is likely that on investigation, the cook is found to be the carrier of -

Accepted Answer

Staphylococcus aureus

Answer

Salmonella typhi

Answer

Vibrio cholerae

Answer

Entamoeba histolytica

Question 10

Which disease is primarily associated with soil as both a source and a reservoir for infection?

Accepted Answer

Tetanus

Answer

Rabies

Answer

Typhoid

Answer

Measles

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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