Infectious Diseases Practice Questions

Q: A positive tuberculin test is indicated by an area of induration of

>10mm in diameter. ***>10mm in diameter*** - For individuals with no known risk factors for TB, an induration of **≥10 mm** is generally considered a **positive tuberculin skin test (TST)**, indicating past exposure to *Mycobacterium tuberculosis*. [1] - This size threshold helps differentiate actual immune responses from non-specific reactions in the general population. *<5mm in diameter* - An induration of **<5 mm** is typically considered **negative** in most populations, indicating no significant immune response to tuberculin. - However, in specific high-risk groups (e.g., HIV-positive individuals, recent contacts of TB patients), an induration of **≥5 mm** might be considered positive. [1] *No induration* - The absence of any induration indicates a **negative tuberculin test**, meaning there is no detectable immune response to the *Mycobacterium tuberculosis* antigens. - This suggests the individual has likely not been exposed to TB or has successfully cleared a prior infection without developing a measurable immune memory. *6-9mm in diameter* - For people with **no risk factors** for TB, this size is generally considered **negative**, indicating no significant immune response. - In certain high-risk groups (e.g., recent immigrants from high-prevalence countries, IV drug users, residents/employees of high-risk settings), an induration of **≥5 mm** can be considered positive. [1]

Q: Best strategy for leprosy eradication programme is

Early diagnosis and treatment. ***Early diagnosis and treatment*** - **Early detection** of leprosy cases and prompt initiation of **multidrug therapy (MDT)** is the cornerstone of leprosy control and eradication programs. - This approach stops transmission by rendering patients non-infectious quickly, preventing further spread of the disease and reducing the incidence of disability. *Mass chemotherapy* - **Mass chemotherapy** involves treating a large population indiscriminately, which is generally not efficient or sustainable for leprosy control. - It could lead to **drug resistance** and unnecessary side effects in individuals who are not infected. *High risk chemotherapy* - **High-risk chemotherapy** typically targets specific populations with known high exposure or vulnerability, which might be a component of control but not the *best* overall strategy for eradication. - It might miss undetected cases outside the defined "high-risk" groups, allowing continued transmission. *Health education* - **Health education** is crucial for increasing awareness, reducing stigma, and promoting early presentation, but by itself, it cannot *control* or *eradicate* the disease. - It is a supportive measure that enhances the effectiveness of medical interventions by encouraging community participation and compliance with treatment.

Q: Which is not used in ORS:

Glucose without salt. ***Glucose without salt*** - **Oral Rehydration Solution (ORS)** formulations specifically include both **glucose and salts (electrolytes)**, as the sodium-glucose co-transport mechanism is crucial for optimal water and electrolyte absorption in the gut. - Using glucose alone without salts would be far less effective for rehydration and replenishing electrolyte losses during conditions like diarrhea. *Glucose with salt* - This combination is the **fundamental basis** of ORS, as **glucose facilitates sodium absorption** and, by extension, water absorption, into the body. - The presence of both glucose and various salts (like sodium chloride, potassium chloride, and sodium citrate) is essential for the efficacy of ORS in **rehydrating and correcting electrolyte imbalances**. *Na+* - **Sodium (Na+)** is a critical electrolyte included in ORS to replace losses and is vital for maintaining fluid balance and various physiological functions. - The correct balance of sodium, along with glucose, is essential for the **co-transport mechanism** that drives water absorption in the intestines. *All of the options* - This option is incorrect because both **glucose with salt (the combination)** and **Na+** are integral components of a standard ORS formulation. - The specific exclusion stated in the question (glucose without salt) is the feature that is *not* used in ORS.

Q: Which microorganism is considered the MOST significant agent for use as a weapon in biological terrorism?

Smallpox. ***Smallpox*** - **Smallpox** is considered a high-priority biological weapon agent due to its **high infectivity**, person-to-person transmission, and high mortality rate. - The discontinuation of global vaccination has led to a population with **minimal immunity**, making it a potent bioweapon. *Influenza* - While influenza viruses are highly transmissible and can cause significant illness, their **mortality rate is generally lower** than agents specifically chosen for biological warfare. - Widespread immunity from natural exposure and annual vaccination campaigns limits its effectiveness as a primary bioweapon. *Ebola* - **Ebola virus** causes severe hemorrhagic fever with a high fatality rate but is typically **less easily transmitted** than agents like smallpox through airborne routes. - Its outbreaks are usually localized, and containment measures are effective in preventing widespread pandemic spread, making it less ideal for mass casualty scenarios compared to smallpox. *Rabies* - **Rabies virus** is transmitted primarily through the bite of an infected animal and is **not easily spread from person to person**. - Its **incubation period is long**, and post-exposure prophylaxis is highly effective, making it an impractical agent for widespread biological terrorism.

Q: "White plague" is

Tuberculosis. ***Tuberculosis*** - This term was historically used for **tuberculosis** due to the characteristic **pallor** and wasting often seen in patients with advanced disease. - It also refers to the widespread and devastating nature of the disease, similar to a "plague," but referring to the chronic emaciation and pale appearance. *Pneumonic Plague* - This is a severe form of **plague** that affects the lungs and is characterized by **rapidly progressing pneumonia**, cough, and shortness of breath. - It does not cause the characteristic pallor or chronic wasting implied by "white plague." *Leprosy* - This is a chronic infectious disease primarily affecting the **skin**, nerves, upper respiratory tract, eyes, and testes. - While it can cause skin lesions and deformities, the term "white plague" is not traditionally associated with leprosy. *Bubonic Plague* - This is the most common form of plague, characterized by **swollen, painful lymph nodes** called "buboes." - It is known for its high mortality rate but does not directly cause the "white" appearance or chronic wasting implied by the term "white plague."

Q: Smallpox eradication was not due to:

Cross-immunity with animal pox virus. ***Cross-immunity with animal pox virus*** - While cowpox provided the basis for the smallpox vaccine, **cross-immunity with naturally circulating animal pox viruses** did not contribute to the eradication of smallpox itself. - The eradication was achieved through targeted vaccination campaigns with a **human-specific vaccine**, not by incidental cross-protection from wildlife. *Highly effective vaccine* - The smallpox vaccine was highly effective, providing **strong and long-lasting immunity** against the Variola virus. - This effectiveness was crucial for establishing herd immunity and breaking the chains of transmission. *Subclinical infections do not transmit the disease* - Individuals infected with smallpox either developed **symptomatic disease** or were **immune/resistant** to infection. - The absence of asymptomatic carriers who could silently transmit the virus made it feasible to interrupt transmission through targeted vaccination and surveillance. *Life long immunity* - Both natural infection and successful vaccination provided **long-lasting, often lifelong immunity** to smallpox. - This durable immunity prevented reinfection and helped sustain the protection achieved through vaccination campaigns over time.

Q: FALSE about Leprosy eradication programme is ?

Long term multi drug therapy. ***Long term multi drug therapy*** - Leprosy eradication programs emphasize **short-term, highly effective multi-drug therapy (MDT)**, not long-term. - The standard duration for paucibacillary leprosy is 6 months and for multibacillary leprosy is 12 months, which is considered short-term given the chronic nature of the disease. *Disability limitation* - This is a crucial component of leprosy programs, focusing on preventing and managing **nerve damage** and its consequences. - Interventions include **early detection of nerve impairment**, protective footwear, and physio-occupational therapy to minimize permanent disabilities. *Health education* - **Health education** is essential for successful eradication, as it increases public awareness, reduces stigma, and promotes early reporting of symptoms. - It also educates patients on the importance of **adherence to MDT** and self-care practices. *Early detection of cases* - **Early detection and prompt treatment** of leprosy cases are fundamental to preventing transmission and reducing the burden of the disease. - This helps to interrupt the chain of infection and prevent the development of severe disabilities.

Q: A 10-year-old boy with dog bite unprovoked comes to you. Appropriate action is:

Give cell culture derived vaccine and rabies immunoglobulin. ***Give cell culture derived vaccine and rabies immunoglobulin*** - An **unprovoked dog bite** carries a high risk of **rabies transmission**, especially in a 10-year-old boy. The most appropriate action is immediate **post-exposure prophylaxis (PEP)**. - **PEP for Category III exposures** (transdermal bites) involves administering a **cell culture-derived rabies vaccine** series along with **rabies immunoglobulin** (RIG) infiltrated into and around the wound, to provide both active and passive immunity. *No further action is necessary* - This option is incorrect and dangerous as **rabies is a fatal disease** once symptoms appear. - An **unprovoked bite** indicates a high suspicion of the dog being rabid, necessitating urgent intervention. *Kill dog and send brain for biopsy* - While testing the animal's brain for rabies is helpful for confirmation, it should **not delay immediate human PEP**, which is critical for survival. - The dog's temperament or rabies status may not be immediately ascertainable, making PEP the priority. *Withhold vaccine and observe dog for 10 days* - Observing the dog for 10 days is a protocol for **low-risk bites from proven healthy dogs that are traceable**, e.g., a pet with known vaccination history. - In cases of **unprovoked bites**, especially from a stray or unknown animal, immediate PEP is mandatory due to the fatal nature of rabies and the unreliability of the observation period in such scenarios.

Q: Which of the following is the most common vector of zoonotic diseases?

Mosquito. ***Mosquito*** - Mosquitoes are responsible for transmitting a vast number of **zoonotic diseases** affecting millions globally, including **malaria**, dengue, Zika, and **West Nile virus**. - Their widespread distribution and ability to feed on various hosts, including humans and animals, make them highly efficient **vectors**. *Sand fly* - Sand flies are known vectors for diseases like **leishmaniasis**, but their reach and impact are not as extensive as mosquitoes. - Leishmaniasis primarily affects specific geographic regions and isn't as globally prevalent as mosquito-borne illnesses. *Ticks* - Ticks transmit several important zoonotic diseases such as **Lyme disease**, Rocky Mountain spotted fever, and ehrlichiosis. - While significant, the global burden of tick-borne diseases is generally less than that of mosquito-borne diseases. *Mite* - Mites can transmit diseases like **scrub typhus** (via chiggers) and are associated with scabies, which is an infestation rather than a direct disease transmission. - Their role as vectors for major zoonotic diseases is comparatively limited.

Q: Hand, foot, and mouth disease is characterized by

Transmitted by virus. ***Transmitted by virus*** - **Hand, foot, and mouth disease (HFMD)** is caused by **enteroviruses**, most commonly Coxsackievirus A16 and enterovirus 71. - These viruses spread readily through **direct contact** with an infected person's nose and throat secretions, blister fluid, or feces. - This is the **most fundamental characteristic** of the disease - its viral etiology. *Incubation period of 3-10 days* - The typical incubation period for HFMD is usually **3 to 7 days**, from exposure to the onset of symptoms. - While 3-10 days is technically accurate as a broader range, it is **not the most defining characteristic** of the disease. *Cause miniepidemic in school* - HFMD is highly contagious and commonly causes **localized outbreaks or "mini-epidemics"** in settings where young children gather, such as schools and daycare centers. - This is a true characteristic of the disease but is **not the most fundamental defining feature** like its viral etiology. *Clinical features similar to those seen in cows* - While there is a disease called "foot-and-mouth disease" in animals (primarily cows, sheep, and pigs), it is caused by a **completely different virus** (an Aphthovirus) and **does not affect humans**. - **Hand, foot, and mouth disease in humans** is entirely distinct and has **no relationship** to the animal disease despite the similar name.

Question 1

A positive tuberculin test is indicated by an area of induration of

Accepted Answer

>10mm in diameter

Answer

<5mm in diameter

Answer

No induration

Answer

6-9mm in diameter

Question 2

Best strategy for leprosy eradication programme is

Accepted Answer

Early diagnosis and treatment

Answer

Mass chemotherapy

Answer

High risk chemotherapy

Answer

Health education

Question 3

Which is not used in ORS:

Accepted Answer

Glucose without salt

Answer

Glucose with salt

Answer

Na+

Answer

All of the options

Question 4

Which microorganism is considered the MOST significant agent for use as a weapon in biological terrorism?

Accepted Answer

Smallpox

Answer

Influenza

Answer

Ebola

Answer

Rabies

Question 5

"White plague" is

Accepted Answer

Tuberculosis

Answer

Pneumonic Plague

Answer

Leprosy

Answer

Bubonic Plague

Question 6

Smallpox eradication was not due to:

Accepted Answer

Cross-immunity with animal pox virus

Answer

Highly effective vaccine

Answer

Subclinical infections do not transmit the disease

Answer

Life long immunity

Question 7

FALSE about Leprosy eradication programme is ?

Accepted Answer

Long term multi drug therapy

Answer

Disability limitation

Answer

Health education

Answer

Early detection of cases

Question 8

A 10-year-old boy with dog bite unprovoked comes to you. Appropriate action is:

Accepted Answer

Give cell culture derived vaccine and rabies immunoglobulin

Answer

No further action is necessary

Answer

Kill dog and send brain for biopsy

Answer

Withhold vaccine and observe dog for 10 days

Question 9

Which of the following is the most common vector of zoonotic diseases?

Accepted Answer

Mosquito

Answer

Sand fly

Answer

Ticks

Answer

Mite

Question 10

Hand, foot, and mouth disease is characterized by

Accepted Answer

Transmitted by virus

Answer

Incubation period of 3-10 days

Answer

Cause miniepidemic in school

Answer

Clinical features similar to those seen in cows

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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