Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 511: All the following are true regarding Dracunculiasis, EXCEPT:

A. Mebendazole and niridazole are effective in preventing the transmission of the disease (Correct Answer)
B. Control of cyclops helps prevent the spread of the disease
C. No effective vaccines are available to prevent the disease
D. The parasites reach adulthood by 10-14 months

Explanation: ***Mebendazole and niridazole are effective in preventing the transmission of the disease*** - There are **no medications** proven to be effective for treating dracunculiasis or preventing its transmission. - Treatment focuses on the **manual extraction** of the worm through gradual winding over days or weeks. *Control of cyclops helps prevent the spread of the disease* - **Dracunculiasis** is transmitted by ingesting **copepods (Cyclops)** infected with **larval Guinea worms** in contaminated water. - Controlling the cyclops population through filtration or chemical treatment of water bodies is a key preventive measure. *No effective vaccines are available to prevent the disease* - Currently, there is **no vaccine** available for human use against Dracunculiasis. - Prevention primarily relies on **safe drinking water access** and behavioral changes. *The parasites reach adulthood by 10-14 months* - The Dracunculus medinensis parasite matures into an adult worm within the human host over a period of **10 to 14 months**. - This long incubation period makes surveillance and intervention challenging.

Question 512: Zoonotic diseases are all except -

A. Q fever
B. Typhoid (Correct Answer)
C. Anthrax
D. Rabies

Explanation: ***Typhoid*** - Typhoid fever is a **bacterial infection** caused by *Salmonella Typhi*, which is spread through contaminated food and water, primarily from human waste. - It is an exclusively **human disease**, meaning there is no animal reservoir involved in its transmission to humans. *Q fever* - Q fever is a **zoonotic disease** caused by the bacterium *Coxiella burnetii*, primarily spread from livestock (cattle, sheep, goats) to humans. - Transmission generally occurs through inhalation of contaminated aerosols from animal excreta or birth products. *Anthrax* - Anthrax is a serious **zoonotic disease** caused by the bacterium *Bacillus anthracis*, which can affect both animals and humans. - Humans usually contract anthrax through contact with infected animals or contaminated animal products. *Rabies* - Rabies is a fatal **viral zoonotic disease** that is transmitted to humans through the saliva of infected animals, most commonly from dog bites. - Wild animals like bats, raccoons, and foxes are important reservoirs for the rabies virus.

Question 513: Isolation period of an infection is important to control its spread. Which of the following is TRUE about the isolation period of enteric fever?

A. Till three bacteriologically negative stools and urine reports (Correct Answer)
B. Till Widal becomes negative
C. Till the fever subsides
D. Upto three days after starting the treatment

Explanation: ***Till three bacteriologically negative stools and urine reports*** - The isolation period for **enteric fever** (typhoid and paratyphoid fever) is determined by the **bacteriological clearance** of the pathogen. - Patients are considered non-infectious when three consecutive **stool and urine cultures** collected at least 24 hours apart are negative for *Salmonella Typhi* or *Paratyphi*. *Till Widal becomes negative* - The **Widal test** detects antibodies against *Salmonella Typhi* and becomes positive during the infection. - However, antibodies can persist for a long time even after the infection has cleared, so a negative Widal test is not an appropriate criterion for ending isolation. *Till the fever subsides* - **Fever subsidence** indicates resolution of acute symptoms but does not guarantee the elimination of the pathogen from the body. - Patients can still be **shedding bacteria** in their stool and urine even after fever has resolved, making them potential sources of infection. *Upto three days after starting the treatment* - While antibiotic treatment reduces the bacterial load, a short duration like three days is usually insufficient for complete **bacteriological clearance**. - Many patients, especially those who become **chronic carriers**, may continue to excrete bacteria for weeks or months even after treatment initiation.

Question 514: Which index is used in relation to Hookworm infestation -

A. Soiling index
B. Quetelet's index
C. Broca's index
D. Chandler's index (Correct Answer)

Explanation: ***Chandler's index*** - Chandler's index is a **soil contamination index** used to assess the level of **hookworm ova** in soil. - It helps determine areas with a high risk of **hookworm transmission** due to poor sanitation and human fecal contamination. *Soiling index* - The soiling index typically refers to the degree of **surface dirtiness** or **atmospheric particulate matter** accumulation. - It is not directly related to helminthic infections or the presence of hookworm ova in the environment. *Quetelet's index* - Quetelet's index is another name for the **Body Mass Index (BMI)**, calculated as weight in kilograms divided by the square of height in meters. - It is used to assess **body fatness** and classify individuals as underweight, normal weight, overweight, or obese, and has no direct relevance to hookworm infestation. *Broca's index* - Broca's index is an older method for calculating **ideal body weight**, typically estimated as height in cm minus 100 or 105. - It is a measure of body weight relative to height and is not used in the context of parasitic infections or environmental contamination.

Question 515: Most important step in cholera control -

A. Water sanitation (Correct Answer)
B. Vaccination
C. Chemoprophylaxis
D. Early treatment

Explanation: ***Water sanitation*** - Cholera is primarily spread through **fecally contaminated water** or food, so ensuring access to safe and clean drinking water is the most crucial preventive measure. - Improved **water purification**, sanitation infrastructure, and proper disposal of human waste directly interrupt the transmission cycle of **Vibrio cholerae**. *Vaccination* - While oral cholera vaccines can provide **temporary protection**, they are generally used as a supplementary measure in outbreak settings or for travelers to endemic areas. - Vaccination alone cannot sustainably control cholera without concurrent improvements in **water and sanitation**. *Chemoprophylaxis* - **Chemoprophylaxis** involves giving antibiotics to prevent infection and is not routinely recommended for cholera control due to concerns about **antibiotic resistance** and its limited impact on population-level transmission. - It is typically reserved for very specific high-risk circumstances, such as close contacts of cholera patients or healthcare workers with direct exposure. *Early treatment* - **Early treatment** with oral rehydration solution (ORS) and, if necessary, antibiotics is vital for reducing mortality among those already infected with cholera. - However, it does not prevent the initial spread of the disease within a community and is not the most important step for overall **disease control and prevention**.

Question 516: True about yellow fever:

A. Incubation period is 10-14 days
B. Incidence is increased by humidity
C. Transmitted by Aedes (Correct Answer)
D. It is found in Asia

Explanation: ***Transmitted by Aedes*** - Yellow fever is primarily transmitted by mosquitoes, specifically species within the genus **Aedes**, such as **Aedes aegypti**. - This vector is responsible for spreading the yellow fever virus between humans and also between non-human primates and humans in jungle cycles. *Incubation period is 10-14 days* - The typical incubation period for yellow fever is shorter, usually **3 to 6 days**, although it can range from 1 to 10 days. - A 10-14 day incubation period is a bit too long for the characteristic onset of symptoms in yellow fever. *Incidence is increased by humidity* - While mosquitoes generally prefer humid environments, the incidence of yellow fever is more directly linked to the **presence of the Aedes mosquito vector** and susceptible human populations, rather than just humidity alone. - Factors like rainfall, temperature, and urbanization are more significant in influencing mosquito breeding and virus transmission. *It is found in Asia* - Yellow fever is **endemic only in tropical and subtropical regions of Africa and South America**. - There has **never been a confirmed outbreak of yellow fever in Asia**, despite the presence of the Aedes aegypti mosquito in the region.

Question 517: Nipah virus is transmitted by

A. Pigs
B. Cattle
C. Fruit bats (Correct Answer)
D. Mosquitoes

Explanation: ***Fruit bats*** - **Fruit bats**, particularly those of the *Pteropus* genus (flying foxes), are the **natural reservoir** for Nipah virus. - The virus is shed in their **urine**, **feces**, and **saliva**, which can then contaminate fruit and other food sources. *Pigs* - **Pigs** can act as **intermediate hosts** and amplify the Nipah virus, transmitting it to humans. - However, they are not the natural reservoir; they become infected by consuming contaminated plant products or interacting with infected bats. *Cattle* - While other livestock, such as **horses** and **goats**, have been shown to be susceptible to Nipah virus infection, **cattle are not typically primary transmitters** to humans. - Their role in Nipah virus epidemiology is generally considered minor compared to bats and pigs. *Mosquitoes* - Nipah virus is **not transmitted by mosquitoes** or other insect vectors. - It is primarily spread through direct contact with infected animals or their bodily fluids, or through contaminated food.

Question 518: All of the following factors are responsible for resurgence of malaria, Except -

A. Use of bed nets (Correct Answer)
B. Drug resistance in the parasite
C. Insecticide resistance in vectors
D. Antigenic mutations in the parasite

Explanation: ***Use of bed nets*** - **Bed nets**, especially those treated with **insecticides**, are a key strategy for **preventing malaria transmission** by creating a physical barrier between humans and mosquitos. - Their widespread use is associated with a **reduction in malaria incidence**, thus they do not contribute to its resurgence but rather help control it. *Antigenic mutations in parasite* - **Antigenic mutations** allow parasites to **evade the host's immune system** and make vaccine development more challenging, contributing to the resurgence of malaria. - These mutations can lead to **new strains** that are not recognized by existing immunity, causing outbreaks in previously protected populations. *Drug Resistance in Parasite* - The development of **drug resistance** in Plasmodium parasites, particularly to common antimalarial drugs like **chloroquine** and **artemisinin-based combination therapies (ACTs)**, is a major factor in malaria resurgence. - Resistant parasites are harder to treat, leading to **increased morbidity and mortality** and sustained transmission. *Insecticide Resistance in vectors* - **Mosquito vectors** developing **resistance to insecticides** used in spraying programs and treated bed nets reduces the effectiveness of these control measures. - This allows mosquito populations to grow and continue transmitting the disease, thereby contributing to **malaria resurgence**.

Question 519: A dentist who got infected with Hepatitis B has recovered from it for the last 3 months. His laboratory tests are normal, but he is not allowed to treat patients. He is known as?

A. Chronic carrier
B. Convalescent carrier (Correct Answer)
C. Active carrier
D. Paradoxical carrier

Explanation: ***Convalescent carrier*** - A **convalescent carrier** is someone who has recovered clinically from an acute infection but continues to harbor and can transmit the pathogen during the recovery period, typically for **weeks to a few months** after apparent recovery. - In Hepatitis B, a convalescent carrier may still have **HBsAg positivity** despite normal liver function tests and clinical recovery, and can transmit the virus during this period. - The scenario describes a dentist who recovered **3 months ago** with normal laboratory tests but is still restricted from treating patients, indicating he remains in the **convalescent carrier phase** and has not yet reached the 6-month threshold for chronic carrier status. - This is why healthcare workers in this phase are temporarily restricted from exposure-prone procedures to prevent transmission. *Chronic carrier* - A **chronic carrier** state for Hepatitis B is defined by the persistence of **HBsAg** (Hepatitis B surface antigen) for **more than 6 months** after acute infection. - While chronic carriers can have normal liver function tests, the key distinguishing feature is the **duration >6 months**, which does not match the **3-month timeline** described in this question. - The dentist has not yet met the temporal criterion for chronic carrier classification. *Active carrier* - The term **active carrier** is not a standard epidemiological classification in medical literature and lacks precise definition. - While both convalescent and chronic carriers can actively transmit disease, the term "active" does not specify the **phase or duration** of the carrier state, which is critical for classification. *Paradoxical carrier* - There is no recognized medical definition for **paradoxical carrier** in epidemiology or infectious disease literature. - This is a distracter with no clinical relevance to carrier state classification.

Question 520: What is the incubation period of measles?

A. 1-4 days
B. 5-7 days
C. 10-14 days (Correct Answer)
D. 15-20 days

Explanation: ***10-14 days*** - The incubation period for **measles** (rubeola) is typically **10 to 14 days** from exposure to the onset of the first symptoms (fever, cough, coryza, conjunctivitis). - The characteristic **Koplik spots** usually appear 2-3 days before the rash, around days 11-12 post-exposure, and the maculopapular rash typically develops 14 days after exposure. *1-4 days* - This period is too short for measles; it's more characteristic of viral illnesses with very rapid onset, like some forms of **influenza** or **common colds**. - A 1-4 day incubation period does not allow for the significant viral replication and initial prodromal symptoms seen in measles. *5-7 days* - While longer than 1-4 days, 5-7 days is still shorter than the typical incubation period for measles. - This range might be seen in some other viral infections, but not measles which has a more extended incubation. *15-20 days* - This period is generally considered too long for the typical incubation of measles. - While there can be slight variations, an incubation period extending to 15-20 days is less common.

Practice by Chapter

Communicable Disease Control Principles

Practice Questions

Vector-Borne Diseases

Practice Questions

Water-Borne Diseases

Practice Questions

Air-Borne Diseases

Practice Questions

Zoonotic Diseases

Practice Questions

Sexually Transmitted Infections

Practice Questions

HIV/AIDS Control Program

Practice Questions

Tuberculosis Control

Practice Questions

Leprosy Elimination

Practice Questions

Emerging and Re-emerging Infections

Practice Questions

Hospital-Acquired Infections

Practice Questions

Integrated Disease Surveillance Project

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free