Infectious Diseases Practice Questions

Q: Which is the only infectious disease that has been eradicated worldwide?

Smallpox. ***Smallpox*** - **Smallpox** was declared eradicated by the World Health Organization in **1980**, following a successful global vaccination campaign. - This was possible due to its **human-only reservoir**, characteristic clinical features, and an effective vaccine. *Polio* - While significant progress has been made towards **polio eradication**, it is not yet fully eradicated, with cases still reported in a few endemic countries. - The disease is caused by the **poliovirus** and is preventable by vaccination, but challenges like vaccine hesitancy and conflict impede full eradication. *Diphtheria* - **Diphtheria** is a serious bacterial infection that is preventable by vaccination and has seen a drastic reduction in cases, but it has not been eradicated worldwide. - Outbreaks still occur in regions with low vaccination coverage, demonstrating its continued presence. *Measles* - **Measles** is a highly contagious viral disease that is preventable by a safe and effective vaccine, but it is far from eradicated. - Outbreaks regularly occur in many parts of the world, especially in areas with suboptimal vaccination rates.

Q: Infectivity of convalescent carrier of cholera lasts for?

2-3 weeks. ***2-3 weeks*** - The infectivity of a **convalescent carrier** of cholera typically lasts for about **2 to 3 weeks** after recovery, according to **Park's Textbook of Preventive and Social Medicine**. - During this period, individuals can still shed **Vibrio cholerae** in their feces, posing a risk of transmission. - This is the **standard duration** taught in Indian medical education for examination purposes. *1-5 days* - This timeframe is too short for the infectivity of a **convalescent carrier**, as bacterial shedding extends well beyond the acute phase. - While symptoms may resolve within this period, the organism continues to be excreted for much longer. *1-2 weeks* - While many individuals may stop shedding within this period (per WHO/CDC data), for examination purposes, the convalescent carrier period is defined as **2-3 weeks**. - This option represents the **lower range** but underestimates the full duration taught in standard Indian textbooks. *4-5 weeks* - This period is too long for the typical infectivity duration of a **convalescent carrier** of cholera. - **Chronic carriers** (rare in cholera, <1% of cases) can shed for months, but this does not represent the convalescent carrier period.

Q: What is the most common source of Diphtheria?

Carrier. ***Carrier*** - **Carriers** (asymptomatic individuals harboring *Corynebacterium diphtheriae*) are the **most common source** of diphtheria transmission. - Carriers outnumber symptomatic cases by a **ratio of 10:1 or more** in the community. - They shed bacteria through **respiratory droplets for weeks to months** without showing symptoms, making them difficult to identify and isolate. - Carriers form the **primary reservoir** that maintains diphtheria transmission in populations, especially in areas with suboptimal immunization coverage. - This is a fundamental epidemiological principle emphasized in Community Medicine. *Infected individual* - While symptomatic infected individuals do transmit diphtheria, they are **less common** as a source compared to carriers. - Symptomatic cases are more likely to be **identified, isolated, and treated** quickly, limiting their transmission potential. - They represent the "tip of the iceberg" in diphtheria epidemiology. *Infected environment* - *Corynebacterium diphtheriae* does not survive for extended periods outside the human host. - Environmental transmission is **extremely rare** and not a significant mode of spread. - Diphtheria is primarily transmitted through **respiratory droplets** (person-to-person contact). *None of the options* - Incorrect, as **carrier** is clearly the most common source of diphtheria.

Q: Which insecticide is commonly used for insecticide-treated bed nets (ITBN) in malaria control?

Deltamethrin. ***Deltamethrin*** - **Deltamethrin** is a synthetic pyrethroid, widely favored for its **low mammalian toxicity** and high efficacy against mosquitoes, making it ideal for ITBNs. - Its **residual action** ensures long-lasting protection against mosquito bites, crucial for effective malaria prevention. *Malathion* - **Malathion** is an organophosphate insecticide and is generally used for **outdoor mosquito control** as a spray, but not typically impregnated into bed nets due to its odor and faster degradation. - It has a higher **acute toxicity** profile compared to pyrethroids, making it less suitable for direct prolonged human contact via bed nets. *Lindane* - **Lindane** (gamma-hexachlorocyclohexane) is an organochlorine insecticide which has been largely **phased out** for public health use due to its persistence in the environment and concerns about its potential neurotoxicity. - It is currently **not recommended** for ITBNs given environmental and health concerns as well as the availability of safer alternatives. *Fenitrothion* - **Fenitrothion** is another organophosphate insecticide primarily used in **agriculture** and for indoor residual spraying (IRS), but it is not commonly used for ITBNs. - Its **higher volatility** and less favorable safety profile compared to pyrethroids limit its use in materials that have direct and prolonged contact with people.

Q: In which disease is a healthy carrier commonly seen?

Meningococcal meningitis. ***Meningococcal meningitis*** - A significant proportion of the population can carry *N. meningitidis* in their **nasopharynx** without developing symptoms, serving as a reservoir for transmission. - This **asymptomatic carriage** is crucial for the spread and persistence of the disease in communities. *Measles* - Measles is highly contagious and typically causes **clear symptoms** in infected individuals; the concept of a healthy, asymptomatic carrier is not relevant. - Individuals with measles are infectious during the **prodromal phase** and until several days after rash onset. *Rubella* - Rubella, while often mild, does not typically involve a **healthy carrier state** where individuals harbor and transmit the virus without symptoms. - Infected individuals usually exhibit a **rash** and mild symptoms, and are contagious during that period. *Influenza* - While individuals can have **asymptomatic or very mild influenza infections**, they are not generally considered **healthy carriers** in the same way as meningococcal disease. - Asymptomatic influenza shedding is usually for a **shorter duration** compared to the prolonged carriage seen with *N. meningitidis*.

Q: What is the primary purpose of taking sewer swabs in public health?

Typhoid carriers in the community. ***Typhoid carriers in the community*** - Sewer swabs are primarily used to detect the presence of **Salmonella Typhi** in sewage, indicating the presence of **asymptomatic carriers** shedding the bacteria. - This method helps identify populations where **typhoid fever** may silently spread or persist due to chronic carriers. *Active typhoid cases in the community* - While sewer swabs can indirectly indicate **active cases** due to increased shedding, their primary purpose is to identify **carriers** who might not be exhibiting symptoms. - **Clinical diagnosis** and **stool culture** from symptomatic individuals are more direct methods for identifying active typhoid cases. *Active cholera cases in the community* - Sewer swabs *can* detect **Vibrio cholerae**, the bacterium causing cholera, but this is not their primary use, especially when targeting **typhoid surveillance**. - **Cholera** outbreaks typically prompt targeted **water sample testing** and clinical surveillance due to their rapid onset and severity. *Cholera carriers in the community* - Similar to active cases, while possible to detect **Vibrio cholerae**, sewer swabs are not the primary tool specifically for identifying **cholera carriers**. - **Cholera carriers** are less common and their detection is usually part of broader environmental surveillance during or after an outbreak.

Q: Which of the following statements about measles is false?

Infectivity is low. ***Infectivity is low*** - Measles is highly contagious, with an **R0 (basic reproduction number)** typically between 12 and 18, making it one of the most infectious human diseases. - Its high infectivity is why **herd immunity** requires a very high vaccination coverage rate (around 95%) to prevent outbreaks. *Koplik's spots is pathognomonic* - **Koplik's spots** are indeed considered **pathognomonic** for measles, appearing as small, white, bluish-white, or grayish lesions on the buccal mucosa opposite the molars. - These spots typically emerge 2-3 days before the characteristic rash and fade as the rash develops. *Measles commonly affects individuals of any age who are not immune.* - Lack of immunity, either through vaccination or previous infection, makes an individual susceptible to measles **regardless of age**. - In developed countries, outbreaks often occur in unvaccinated populations or those with waning immunity, as seen in adults who may not have received measles vaccines or caught the infection as children. *The source of infection is typically an infected person* - Measles is an **airborne disease** spread through respiratory droplets from an infected person's coughing and sneezing. - The virus can live for up to two hours in the air or on surfaces, making direct contact with an infected individual or their respiratory secretions the primary mode of transmission.

Q: What is the primary causative vector of Vagabond disease?

Louse. ***Louse*** - Vagabond disease is a term historically used to describe the chronic skin changes (such as **pigmentation**, **lichenification**, and **excoriations**) resulting from persistent **pediculosis corporis** (body lice infestation). - The **body louse** (*Pediculus humanus corporis*) is the causative agent responsible for these chronic dermatological changes through prolonged infestation. - Body lice are also vectors that can transmit other diseases like **epidemic typhus**, **louse-borne relapsing fever**, and **trench fever**, but vagabond disease itself is the direct result of chronic louse infestation rather than a transmitted pathogen. *Mite* - Mites are responsible for various conditions, such as **scabies** (caused by *Sarcoptes scabiei*) and serve as vectors for **scrub typhus** (transmitted by chiggers, the larval form of trombiculid mites). - However, they are not associated with vagabond disease or the chronic dermatological changes caused by body lice. *Tick* - Ticks are known vectors for a wide range of diseases, including **Lyme disease**, **Rocky Mountain spotted fever**, **anaplasmosis**, and **babesiosis**. - These diseases are transmitted through the bite of infected ticks, which are distinct from the louse-related conditions associated with vagabond disease. *Black Fly* - Black flies (*Simulium* species) are vectors for **onchocerciasis** (river blindness), caused by the parasitic nematode *Onchocerca volvulus*. - While they can cause itchy bites and transmit significant disease, they are not involved in the chronic skin condition known as vagabond disease.

Q: According to RNTCP guidelines, what should be done first in a TB suspect case?

Sputum microscopy. ***Sputum microscopy*** - Under the Revised National Tuberculosis Control Programme (RNTCP) guidelines, **sputum smear microscopy** is the initial and primary diagnostic tool for identifying pulmonary TB in suspect cases. - It is a **cost-effective and rapid method** for detecting **acid-fast bacilli (AFB)** directly from sputum samples. *Chest X-ray* - While a Chest X-ray can show abnormalities consistent with TB, it is often used as a **supplementary diagnostic tool** after initial sputum tests. - It is **less specific** than sputum microscopy for confirming active TB and requires further confirmation with microbiological tests. *Sputum culture* - Sputum culture is a **more sensitive diagnostic method** for TB compared to microscopy, but it takes **several weeks** for results. - It is typically used when smear microscopy results are negative but there is a strong clinical suspicion of TB, or for **drug susceptibility testing**. *Start short-course chemotherapy* - Initiating short-course chemotherapy **without confirming the diagnosis** is not recommended and can lead to antibiotic resistance and inappropriate treatment. - Treatment should only be started after a **confirmed diagnosis** of active TB through microbiological tests like sputum microscopy or culture.

Q: Post exposure prophylaxis is not indicated in which of the following conditions?

Typhoid. ***Typhoid*** - **Post-exposure prophylaxis (PEP)** is generally **not indicated** for typhoid fever, as **antibiotic treatment** is highly effective once symptoms develop. - Prevention primarily involves **vaccination** and ensuring **safe food and water hygiene**, not medication after exposure. *Rabies* - **PEP is crucial** for rabies due to its nearly 100% fatality rate once symptoms appear, involving **vaccine** and **immunoglobulin** administration. - Exposure typically occurs through bites or scratches from **rabid animals**. *Chickenpox* - **PEP** with **VariZIG (varicella zoster immune globulin)** or **antiviral medications** may be indicated for high-risk individuals after exposure. - This is primarily to prevent severe disease in **immunocompromised individuals** or pregnant women without immunity. *Measles* - **PEP** with the **measles vaccine** or **immunoglobulin (IG)** is recommended for susceptible individuals exposed to measles. - This intervention can **prevent or modify the course** of the disease, especially in unvaccinated contacts.

Question 1

Which is the only infectious disease that has been eradicated worldwide?

Accepted Answer

Smallpox

Answer

Polio

Answer

Diphtheria

Answer

Measles

Question 2

Infectivity of convalescent carrier of cholera lasts for?

Accepted Answer

2-3 weeks

Answer

1-5 days

Answer

1-2 weeks

Answer

4-5 weeks

Question 3

What is the most common source of Diphtheria?

Accepted Answer

Carrier

Answer

Infected environment

Answer

Infected individual

Answer

None of the options

Question 4

Which insecticide is commonly used for insecticide-treated bed nets (ITBN) in malaria control?

Accepted Answer

Deltamethrin

Answer

Malathion

Answer

Fenitrothion

Answer

Lindane

Question 5

In which disease is a healthy carrier commonly seen?

Accepted Answer

Meningococcal meningitis

Answer

Measles

Answer

Rubella

Answer

Influenza

Question 6

What is the primary purpose of taking sewer swabs in public health?

Accepted Answer

Typhoid carriers in the community

Answer

Active typhoid cases in the community

Answer

Active cholera cases in the community

Answer

Cholera carriers in the community

Question 7

Which of the following statements about measles is false?

Accepted Answer

Infectivity is low

Answer

Measles commonly affects individuals of any age who are not immune.

Answer

Koplik's spots are pathognomonic

Answer

The source of infection is typically an infected person

Question 8

What is the primary causative vector of Vagabond disease?

Accepted Answer

Louse

Answer

Mite

Answer

Tick

Answer

Black Fly

Question 9

According to RNTCP guidelines, what should be done first in a TB suspect case?

Accepted Answer

Sputum microscopy

Answer

Chest X-ray

Answer

Sputum culture

Answer

Start short-course chemotherapy

Question 10

Post exposure prophylaxis is not indicated in which of the following conditions?

Accepted Answer

Typhoid

Answer

Rabies

Answer

Chickenpox

Answer

Measles

Infectious Diseases — MCQs

Infectious Diseases — MCQs

On this page

Practice by Chapter

Want unlimited practice?