Infectious Diseases Practice Questions

Q: Zoonotic diseases are all except -

Typhoid. ***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.

Q: Which index is used in relation to Hookworm infestation -

Chandler's index. ***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.

Q: Which of the following is true of typhoid?

Female carriers are more common than male carriers. Female carriers are more common than male carriers - **Chronic carriage** of *Salmonella Typhi* is notably more prevalent in **women** than in men, often due to hormonal factors or gender-specific immunological differences influencing bacterial persistence. - This observation has significant implications for public health strategies focused on identifying and managing **chronic carriers** to prevent disease transmission. *Tetracycline is the drug of choice for treating carriers* - **Tetracyclines** are generally not the drug of choice for treating **typhoid carriers**; quinolones like **ciprofloxacin** or **azithromycin** are preferred due to better efficacy against intracellular *Salmonella Typhi*. - The effectiveness of **tetracyclines** against *Salmonella Typhi* can be limited by **antibiotic resistance** and suboptimal penetration into the gallbladder where bacteria often persist. *Gallbladder is rarely involved in the chronic carrier state* - The **gallbladder** is the primary anatomical site for **chronic carriage** of *Salmonella Typhi*, as bacteria can colonize the bile ducts and form biofilms, making eradication difficult. - Involvement of the **gallbladder** is crucial for understanding disease transmission, as carries intermittently shed bacteria in their feces [1]. *Chronic carriage is more common in young males* - **Chronic carriage** of *Salmonella Typhi* is more frequently observed in **older individuals**, particularly **older women**, rather than young males. - Age and gender are identified risk factors, with **postmenopausal women** having a higher propensity for developing a chronic carrier state.

Q: Most important step in cholera control -

Water sanitation. ***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**.

Q: True about yellow fever:

Transmitted by Aedes. ***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.

Q: Major signs for AIDS case definition according to WHO is-

Prolonged fever more than 1 month. Prolonged fever more than 1 month - Prolonged unexplained fever (intermittent or constant) lasting for more than 1 month is a major clinical sign for AIDS case definition according to the WHO clinical staging system for adults and adolescents. - This symptom reflects the chronic systemic inflammation and immune dysregulation characteristic of advanced HIV infection [1]. Prolonged cough for > 1 month - While chronic cough can be a minor sign or an indicator of opportunistic infections like tuberculosis or Pneumocystis pneumonia in HIV-positive individuals, it is not listed as a major sign for the WHO AIDS case definition [1], [2]. - Major signs are those considered to be strong indicators of severe immunodeficiency. Generalized lymphadenopathy - Persistent generalized lymphadenopathy (PGL) is a common finding in early and mid-stage HIV infection, often indicating viral replication but not necessarily advanced immunodeficiency [1]. - It is classified as an HIV clinical stage 1 condition by the WHO, meaning it’s not a major sign for AIDS [1]. Generalized pruritic dermatitis - Generalized pruritic papular eruptions or severe pruritic dermatitis are considered clinical conditions defining WHO clinical stage 2 or stage 3 HIV disease, respectively [1]. - While these can be prominent symptoms, they are not categorized as the primary "major signs" used for the fundamental AIDS case definition as fever or severe weight loss.

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

Use of bed nets. ***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**.

Q: Brucellosis can be transmitted by all of the following modes, except -

Person to person transmission. ***Person to person transmission*** - **Person-to-person transmission is NOT a significant route** for brucellosis and is the correct answer for this "except" question. - Brucellosis is primarily a **zoonotic disease**, transmitted from infected animals to humans. - While extremely rare instances have been reported (sexual transmission, organ transplantation, breastfeeding), these are **not epidemiologically significant** routes. - The disease does **not spread readily between humans** like typical communicable diseases. *Inhalation of infected dust or aerosol* - **Inhalation** of contaminated aerosols is a well-documented transmission route. - Common among **abattoir workers, laboratory personnel, and veterinarians** handling infected animal specimens. - The bacteria can enter through the **respiratory tract** and cause infection. *Contact with infected placenta* - **Direct contact with infected animal tissues** (placentas, aborted fetuses, birth fluids) is a **major transmission route**. - Occupational exposure for **farmers, veterinarians, and slaughterhouse workers**. - Bacteria enter through **skin abrasions or mucous membranes**. *Ingestion of unpasteurized milk and dairy products* - **Ingestion of contaminated food** is the **most common transmission route** worldwide. - Unpasteurized **milk, cheese, and other dairy products** from infected animals (cattle, goats, sheep) are the primary vehicles. - This is why **pasteurization** is critical for preventing brucellosis in the general population.

Q: The infectivity of a convalescent case of cholera lasts for

7-14 days. ***7-14 days*** - The infectivity of a convalescent case of **cholera** typically lasts for **7 to 14 days** after the onset of symptoms, during which time the individual continues to shed *Vibrio cholerae* in their feces. - This is the **most common duration** of bacterial shedding in convalescent cholera patients, as documented in standard epidemiological references including Park's Textbook of Preventive and Social Medicine. - This period is critical for public health measures, as convalescent carriers can still transmit the disease, especially in areas with poor sanitation. - After appropriate antibiotic treatment, the duration may be shortened to **3-5 days**. *14-21 days* - While some individuals may continue to shed *Vibrio cholerae* for **14-21 days**, this represents an **extended or atypical duration** rather than the typical convalescent period. - This longer shedding period may occur in patients with delayed treatment or incomplete antibiotic therapy, but is not the standard expected duration. - The typical duration of infectivity is shorter, usually resolving within **2 weeks**. *Less than 7 days* - While antibiotic treatment (especially with doxycycline or azithromycin) can significantly shorten the duration of bacterial shedding to **3-5 days**, most untreated or partially treated convalescent cases continue to shed for at least a week. - This duration is **too short** to represent the typical convalescent carrier period without aggressive antimicrobial therapy. *21-28 days* - Shedding beyond **21 days** is uncommon and represents **chronic carrier status**, which is rare with cholera (unlike typhoid fever where chronic carriers are more common). - Prolonged shedding for 3-4 weeks may occur in immunocompromised individuals or those with underlying gallbladder disease, but this is not the typical pattern for convalescent cholera cases. - The vast majority of patients clear the organism within **2 weeks** of symptom onset.

Question 1

Zoonotic diseases are all except -

Accepted Answer

Typhoid

Answer

Q fever

Answer

Anthrax

Answer

Rabies

Question 2

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

Accepted Answer

Till three bacteriologically negative stools and urine reports

Answer

Till Widal becomes negative

Answer

Till the fever subsides

Answer

Upto three days after starting the treatment

Question 3

Which index is used in relation to Hookworm infestation -

Accepted Answer

Chandler's index

Answer

Soiling index

Answer

Quetelet's index

Answer

Broca's index

Question 4

Which of the following is true of typhoid?

Accepted Answer

Female carriers are more common than male carriers

Answer

Tetracycline is the drug of choice for treating carriers

Answer

Gallbladder is rarely involved in the chronic carrier state

Answer

Chronic carriage is more common in young males

Question 5

Most important step in cholera control -

Accepted Answer

Water sanitation

Answer

Vaccination

Answer

Chemoprophylaxis

Answer

Early treatment

Question 6

True about yellow fever:

Accepted Answer

Transmitted by Aedes

Answer

Incubation period is 10-14 days

Answer

Incidence is increased by humidity

Answer

It is found in Asia

Question 7

Major signs for AIDS case definition according to WHO is-

Accepted Answer

Prolonged fever more than 1 month

Answer

Prolonged cough for > 1 month

Answer

Generalized lymphadenopathy

Answer

Generalized pruritic dermatitis

Question 8

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

Accepted Answer

Use of bed nets

Answer

Drug resistance in the parasite

Answer

Insecticide resistance in vectors

Answer

Antigenic mutations in the parasite

Question 9

Brucellosis can be transmitted by all of the following modes, except -

Accepted Answer

Person to person transmission

Answer

Inhalation of infected dust or aerosol

Answer

Contact with infected placenta

Answer

Ingestion of unpasteurized milk and dairy products

Question 10

The infectivity of a convalescent case of cholera lasts for

Accepted Answer

7-14 days

Answer

14-21 days

Answer

21-28 days

Answer

Less than 7 days

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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