Infectious Diseases Practice Questions

Q: According to DOTS strategy, what is the criterion for diagnosis of tuberculosis?

2 out of 3 samples positive. ***2 out of 3 samples positive*** - Under the **DOTS (Directly Observed Treatment, Short-course) strategy**, a diagnosis of **pulmonary tuberculosis** is confirmed when at least **two out of three sputum smear samples** are positive for acid-fast bacilli (AFB). - This criterion aims to balance diagnostic accuracy with the feasibility of rapid and efficient diagnosis in resource-limited settings. *3 out of 3 samples positive* - Requiring all three samples to be positive would be more stringent and might lead to **delayed diagnosis** or **missed cases**, especially in individuals with lower bacillary loads. - While highly specific, it is not the standard criterion for initial diagnosis under DOTS, which prioritizes timely treatment. *1 out of 2 samples positive* - This criterion would be **less specific** and could result in a higher rate of **false positives**, leading to unnecessary treatment and potential side effects. - The DOTS strategy aims for a reliable diagnosis with a reasonable level of certainty before initiating a lengthy and potent drug regimen. *None of the options* - This option is incorrect because there is a specific, well-established criterion within the DOTS strategy for diagnosing pulmonary tuberculosis based on sputum smear microscopy results. - The framework provides clear guidelines for diagnosis and treatment to ensure effective control of the disease globally.

Q: The most common way in which tuberculosis is acquired is via the

Respiratory tract. ***Respiratory tract*** - **Tuberculosis (TB)** is primarily transmitted through **airborne droplets** generated when an infected person coughs, sneezes, or speaks. - Inhalation of these droplets containing **Mycobacterium tuberculosis** leads to infection, making the respiratory tract the most common route. *Genital tract* - While TB can affect the genital tract (e.g., **genital tuberculosis**), it is a rare manifestation and not the primary mode of transmission. - Genital tract involvement usually occurs via **hematogenous spread** from a primary pulmonary focus, not direct acquisition. *Gastrointestinal tract* - **Gastrointestinal TB** can occur through ingestion of contaminated milk (historically **Mycobacterium bovis**) or sputum containing **Mycobacterium tuberculosis**. - However, this is far less common than respiratory transmission, especially in modern settings with pasteurization. *Skin* - **Cutaneous TB** can occur through direct inoculation of the skin, but this is a very rare form of transmission. - It usually presents as specific skin lesions and is not the predominant way in which TB is acquired by the general population.

Q: Culex mosquito transmits:

Japanese encephalitis. ***Japanese encephalitis*** * **Culex mosquitoes** are the primary vectors for the **Japanese encephalitis virus** (JEV), a flavivirus. * JEV is a significant cause of **viral encephalitis** in Asia, largely transmitted by Culex species such as *Culex tritaeniorhynchus*. *Dengue fever* * Dengue fever is primarily transmitted by mosquitoes of the genus ***Aedes***, particularly *Aedes aegypti* and *Aedes albopictus*. * These mosquitoes are known for biting during the **daytime** and are common in urban and semi-urban areas. *Tularemia* * Tularemia is caused by the bacterium *Francisella tularensis* and is primarily transmitted by **ticks**, deer flies, or direct contact with infected animals. * Mosquitoes are **not a primary vector** for the transmission of tularemia. *Yellow fever* * Yellow fever is primarily transmitted by mosquitoes of the genus ***Aedes***, particularly *Aedes aegypti*. * This viral hemorrhagic fever is common in tropical and subtropical regions of South America and Africa.

Q: A patient who was initially smear positive, who began the treatment and who remained or became smear positive again at five months or later during the course of treatment is called as:

Treatment failure. ***Treatment failure*** - This definition accurately describes a patient who was initially **smear positive**, began treatment, and remained or became **smear positive again at five months or later** during the course of treatment. - It indicates that the current anti-tuberculosis regimen is insufficient to clear the bacterial load, often due to **drug resistance** or poor adherence. *Relapse* - A relapse refers to a patient who successfully completed their anti-tuberculosis treatment, was declared cured, but subsequently developed **tuberculosis again**. - The key differentiator is the prior completion of treatment and declaration of cure, which is not the case in the scenario described. *Defaulter* - A defaulter is a patient who has **interrupted their treatment for two consecutive months or more** after having been on treatment for at least one month. - This definition focuses on the interruption of treatment, not the persistent or recurrent smear positivity while actively undergoing treatment. *None of the options* - This option is incorrect because "Treatment failure" accurately describes the scenario presented.

Q: In dengue surveillance, indices that are commonly used to monitor Aedes aegypti infestation levels are all, EXCEPT:

Street index. ***Street index*** - The **Street index** is not a standard entomological index used for monitoring *Aedes aegypti* infestation levels or density in dengue surveillance. - Surveillance efforts typically focus on household-level indices to assess mosquito breeding sites. *House index* - The **House index** (HI) measures the percentage of houses infested with *Aedes* larvae and/or pupae. - It provides an indication of the proportion of dwellings in an area that serve as mosquito breeding sites. *Breteau index* - The **Breteau index** (BI) calculates the number of positive containers per 100 houses inspected. - It reflects the density of breeding containers and is considered a more sensitive indicator of mosquito population density than the House index. *Pupae index* - The **Pupae index** (PI) measures the average number of pupae per person or per house. - This index is highly correlated with adult mosquito density and is considered the most accurate indicator of potential dengue transmission risk.

Q: Pig serves as an amplifier host for -

Japanese encephalitis. ***Japanese encephalitis*** * **Pigs** serve as the primary **amplifying hosts** for the Japanese encephalitis virus (JEV), meaning the virus replicates to high titers in them, increasing the potential for mosquito transmission. * Mosquitoes, particularly *Culex tritaeniorhynchus*, feed on infected pigs and then transmit the virus to humans and other animals. *West Nile fever* * The main **amplifying hosts** for West Nile virus are **birds**, particularly corvids. * Humans and horses are **dead-end hosts**, meaning the virus does not replicate to high enough levels in them to sustain mosquito transmission. *Yellow fever* * The primary reservoir and **amplifying hosts** for yellow fever virus are **monkeys** in sylvatic cycles. * Humans are also infected, but mosquitoes primarily transmit the virus between monkeys or from monkeys to humans. *KFD* * **Kyasanur Forest Disease** is primarily maintained in a cycle involving **ticks** and small **rodents** and **monkeys**, which act as amplifying hosts. * Humans become infected through tick bites, particularly from *Haemaphysalis spinigera*.

Q: Indicator for outbreak of Plague epidemic is

Cheopis index. ***Cheopis index*** - The **Cheopis index** (or **flea index**) measures the average number of *Xenopsylla cheopis* (oriental rat flea) per rat, which is the primary vector for **bubonic plague**. - A Cheopis index of **1 or more** indicates a high risk of a plague outbreak, as it suggests a significant number of infected fleas are present on the rat population. *Rat burrow index* - The **rat burrow index** indicates the density of rat activity by counting active burrows, but it does not directly measure the **flea burden** or infection risk. - While high rat density can indirectly increase risk, it's not as specific an indicator for **plague transmission** as the Cheopis index. *Total flea* - **Total flea count** refers to the absolute number of fleas collected, but it doesn't account for the **rat population size** or the specific vector species (*Xenopsylla cheopis*). - A high total flea count might simply reflect a large rat population rather than an elevated risk of **plague transmission**. *Specific flea index* - The term **specific flea index** is less commonly used in the context of plague surveillance compared to the **Cheopis index**, which specifically targets the primary vector. - It could be interpreted as similar to the Cheopis index but lacks the precise and globally recognized definition used for **plague risk assessment**.

Q: Leprosy commonly spreads by:

Droplet. ***Droplet*** - Leprosy is primarily transmitted through **respiratory droplets** expelled during coughing or sneezing by an untreated person with **multibacillary leprosy**. - **Prolonged, close contact** with an infected individual is typically required for transmission due to the slow growth rate of *Mycobacterium leprae*. *Water* - Diseases spread through water, such as **cholera** or **typhoid**, are often caused by the ingestion of contaminated water containing pathogens. - Leprosy is not a **waterborne disease**; its transmission route is different. *Milk* - **Milk-borne diseases** are typically contracted by consuming raw or unpasteurized milk contaminated with bacteria like *Listeria* or *Brucella*. - Leprosy is not transmitted via **ingestion of milk** or dairy products. *Mosquitoes* - Mosquitoes are vectors for diseases such as **malaria**, **dengue**, and **Zika virus**, transmitting pathogens through bites. - Leprosy is not an **arthropod-borne disease** and is not spread by insect bites.

Q: Which of the following diseases is spread by mosquitoes?

Dengue. ***Dengue*** is the correct answer. - **Dengue fever** is a **mosquito-borne** viral disease transmitted primarily by **Aedes aegypti** and **Aedes albopictus** mosquitoes. - Symptoms range from mild flu-like illness to severe dengue hemorrhagic fever or dengue shock syndrome. *Listeriosis* - Caused by **Listeria monocytogenes**, transmitted through contaminated food consumption. - **Not spread by mosquitoes** but through foodborne routes or contact with infected animals. *Kala azar* - Visceral leishmaniasis caused by **Leishmania parasites**, transmitted by infected **sandflies**, not mosquitoes. - Affects internal organs including spleen, liver, and bone marrow. *Trypanosomiasis* - Includes **African sleeping sickness** (transmitted by **tsetse flies**) and **Chagas disease** (transmitted by **reduviid bugs/kissing bugs**). - Neither vector is a mosquito.

Q: Molar ratio of Sodium and Glucose in WHO ORS is:

1:1. ***1:1*** - The **WHO Low-Osmolarity ORS** (recommended since 2002) contains **75 mmol/L of both sodium and glucose**, resulting in a **1:1 molar ratio**. - This formulation is based on the principle of **sodium-glucose co-transport** across the intestinal mucosa, where glucose facilitates sodium absorption, and water follows passively. - The 1:1 ratio in the low-osmolarity formulation (total osmolarity ~245 mOsm/L) has been shown to **reduce stool output by 20%** and **decrease the need for IV therapy by 33%** compared to the older standard ORS. - This is the **current WHO and UNICEF recommendation** for managing acute diarrhea. *1:2* - This ratio is **not used in WHO ORS formulations**. - A higher glucose concentration relative to sodium would create a more **hyperosmolar solution**, potentially worsening osmotic diarrhea. - This does not represent any standard ORS formulation. *2:1* - A 2:1 ratio of sodium to glucose would provide **excessive sodium** relative to glucose. - This would result in a **hypertonic solution** that could draw water into the intestinal lumen, potentially worsening dehydration. - The sodium-glucose co-transport mechanism works optimally when both are present in **balanced proportions**. *1:4* - This ratio implies **excessive glucose** relative to sodium (4 times more glucose than sodium). - High glucose concentration would create significant **osmotic load**, potentially causing osmotic diarrhea. - The **reduced sodium content** would be insufficient for effective rehydration and electrolyte replacement in diarrheal diseases.

Question 1

According to DOTS strategy, what is the criterion for diagnosis of tuberculosis?

Accepted Answer

2 out of 3 samples positive

Answer

3 out of 3 samples positive

Answer

1 out of 2 samples positive

Answer

None of the options

Question 2

The most common way in which tuberculosis is acquired is via the

Accepted Answer

Respiratory tract

Answer

Genital tract

Answer

Gastrointestinal tract

Answer

Skin

Question 3

Culex mosquito transmits:

Accepted Answer

Japanese encephalitis

Answer

Dengue fever

Answer

Tularemia

Answer

Yellow fever

Question 4

A patient who was initially smear positive, who began the treatment and who remained or became smear positive again at five months or later during the course of treatment is called as:

Accepted Answer

Treatment failure

Answer

Relapse

Answer

Defaulter

Answer

None of the options

Question 5

In dengue surveillance, indices that are commonly used to monitor Aedes aegypti infestation levels are all, EXCEPT:

Accepted Answer

Street index

Answer

House index

Answer

Breteau index

Answer

Pupae index

Question 6

Pig serves as an amplifier host for -

Accepted Answer

Japanese encephalitis

Answer

West Nile fever

Answer

Yellow fever

Answer

KFD

Question 7

Indicator for outbreak of Plague epidemic is

Accepted Answer

Cheopis index

Answer

Rat burrow index

Answer

Total flea

Answer

Specific flea index

Question 8

Leprosy commonly spreads by:

Accepted Answer

Droplet

Answer

Water

Answer

Milk

Answer

Mosquitoes

Question 9

Which of the following diseases is spread by mosquitoes?

Accepted Answer

Dengue

Answer

Listeriosis

Answer

Kala azar

Answer

Trypanosomiasis

Question 10

Molar ratio of Sodium and Glucose in WHO ORS is:

Accepted Answer

1:1

Answer

1:2

Answer

2:1

Answer

1:4

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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