Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 381: Kala azar is spread by –

A. Black–fly
B. Sand–fly (Correct Answer)
C. Tsetse–fly
D. House–fly

Explanation: ***Sand–fly*** - Kala-azar, also known as **visceral leishmaniasis**, is transmitted to humans through the bite of an infected female **Phlebotomine sandfly**. - The sandfly acts as a **biological vector**, harboring the **Leishmania parasites** in its gut. *Black–fly* - **Black flies** are vectors for **onchocerciasis** (river blindness), caused by the parasite *Onchocerca volvulus*. - They are typically found near **fast-flowing water** and their bites often lead to skin nodules and eye lesions. *Tsetse–fly* - The **tsetse fly** is the vector for **African trypanosomiasis** (sleeping sickness), caused by species of *Trypanosoma*. - This disease primarily affects central nervous system function, leading to changes in sleep patterns. *House–fly* - **House flies** are primarily **mechanical vectors** for various pathogens, meaning they can transfer microbes from contaminated surfaces to food. - They are not known to transmit specific diseases like Kala-azar through a bite.

Question 382: Risk of transmission from single percutaneous exposure to blood for HIV is:-

A. 2.7-10%
B. 6-30%
C. 0.1 - 0.36% (Correct Answer)
D. 0.4-5%

Explanation: ***0.1 - 0.36%*** - The risk of **HIV transmission** from a single percutaneous exposure (e.g., needle stick injury) to infected blood is approximately **0.3%** (range 0.1% to 0.36%) according to CDC guidelines. - This relatively low risk is due to the small inoculum size and lower viral concentration in needle stick injuries compared to other exposures. - Post-exposure prophylaxis (PEP) can further reduce this already low transmission risk. *2.7-10%* - This range is significantly **higher** than the established risk for percutaneous HIV transmission. - This percentage is more aligned with **Hepatitis C virus (HCV)** transmission risk, which is approximately 1.8% (range 0-7%). *6-30%* - This range is substantially **overstated** for HIV transmission from percutaneous exposure. - These percentages reflect the transmission risk for **Hepatitis B virus (HBV)**, which has a much higher transmission rate (6-30%) from needle stick injuries. *0.4-5%* - While 0.4% is close to some reported upper limits, the 5% figure is **much higher** than established estimates for percutaneous HIV transmission. - This range incorrectly combines different risk estimates and does not accurately represent single percutaneous HIV exposure risk.

Question 383: ICD-10 chapter 1 describes?

A. Poisoning and consequences
B. Psychiatric diseases
C. Diseases of the nervous system
D. Infectious and parasitic diseases (Correct Answer)

Explanation: ***Infectious and parasitic diseases*** - **ICD-10 Chapter 1** specifically categorizes codes related to **infectious and parasitic diseases**, ranging from A00 to B99. - This chapter covers a broad spectrum of conditions caused by microorganisms and parasites, such as bacterial, viral, fungal, and protozoal infections. *Poisoning and consequences* - **Poisoning and certain other consequences of external causes** are covered in ICD-10 Chapter 19, with codes typically ranging from T36-T65 for poisoning by drugs, medicaments, and biological substances. - This chapter focuses on injuries, poisoning, and certain other consequences of external causes, not infectious diseases. *Psychiatric diseases* - **Mental and behavioral disorders** (often referred to as psychiatric diseases) are described in ICD-10 Chapter 5, with codes ranging from F00 to F99. - This chapter includes conditions such as mood disorders, anxiety disorders, schizophrenia, and substance-related disorders. *Diseases of the nervous system* - **Diseases of the nervous system** are categorized in ICD-10 Chapter 6, with codes ranging from G00 to G99. - This chapter covers conditions affecting the brain, spinal cord, nerves, and neuromuscular junctions, such as stroke, epilepsy, and Parkinson's disease.

Question 384: A person with tuberculosis on domiciliary treatment is expected to do all, except?

A. Collect drugs regularly
B. Dispose sputum safely
C. Use separate vessels (Correct Answer)
D. Report to PHC if new symptoms arise

Explanation: ***Use separate vessels*** - **Tuberculosis** is primarily spread through airborne droplets, not through shared utensils. - While good hygiene is important, using separate dishes is not a specific requirement for preventing transmission in a household setting and is not routinely advised. *Collect drugs regularly* - **Regular collection and adherence to drug therapy** are crucial for treatment success and preventing drug resistance in tuberculosis. - Interrupted treatment can lead to **treatment failure** and spread of the disease. *Dispose sputum safely* - **Sputum** from a person with active tuberculosis contains the bacteria and can be a source of airborne transmission. - Proper disposal, such as in a covered container that is then sterilized or discarded safely, helps prevent the spread of infection. *Report to PHC if new symptoms arise* - **Close monitoring** for new or worsening symptoms is essential to identify potential side effects of medication, treatment failure, or development of complications. - Reporting to a **Primary Health Centre (PHC)** ensures timely medical review and management.

Question 385: Zoonotic diseases are -

A. Anthrax
B. Plague
C. Salmonellosis
D. All of the options (Correct Answer)

Explanation: ***All of the options*** - **Anthrax**, **Plague**, and **Salmonellosis** are all well-established examples of zoonotic diseases, which are infections naturally transmitted between vertebrate animals and humans. - These diseases represent a diverse spectrum of bacterial infections with significant public health implications worldwide. **Anthrax** - Caused by *Bacillus anthracis*, a spore-forming bacterium naturally found in soil that primarily affects livestock and wild herbivores. - Humans acquire infection through contact with infected animals or contaminated animal products (hides, wool, meat). - Clinical forms include cutaneous (most common), inhalational (most severe), and gastrointestinal anthrax. - Remains an important occupational hazard for veterinarians, farmers, and those handling animal products. **Plague** - Caused by *Yersinia pestis*, maintained in nature through rodent-flea cycles. - Transmission to humans occurs primarily via bites from infected fleas or direct contact with infected animals. - Historically responsible for devastating pandemics including the Black Death. - Clinical manifestations include bubonic (most common), pneumonic (person-to-person transmission possible), and septicemic plague. **Salmonellosis** - Caused by non-typhoidal *Salmonella* species, commonly colonizing the intestines of various animals including poultry, cattle, reptiles, and pets. - Humans typically acquire infection through consumption of contaminated food (undercooked meat, eggs, unpasteurized dairy) or direct animal contact. - Presents as acute gastroenteritis with diarrhea, fever, and abdominal cramps. - One of the most common foodborne zoonotic infections globally.

Question 386: Which of the following is NOT true about varicella infection?

A. Lesions occur on flexor surfaces
B. Secondary attack rate is 90%
C. Only single stage of lesion is present at a time (Correct Answer)
D. Reactivation occurs in 10-30% of cases

Explanation: ***Only single stage of lesion is present at a time*** - This statement is **incorrect** and represents the key distinguishing feature that makes this the answer. - Varicella (chickenpox) is classically characterized by **pleomorphism** - lesions in various stages of development (macules, papules, vesicles, pustules, and crusts) appearing **simultaneously** on the body. - This "multiple stages at once" phenomenon is a pathognomonic diagnostic feature of chickenpox, differentiating it from other vesicular rashes like smallpox (which shows uniform stage lesions). *Lesions occur on flexor surfaces* - This statement is **not a defining characteristic** of varicella, though it is not entirely false either. - Varicella typically has a **centripetal distribution** - lesions predominantly affect the **trunk and face**, with relative sparing of distal extremities. - Unlike conditions such as atopic dermatitis, varicella does **not** have a specific predilection for flexor versus extensor surfaces. - While lesions may appear on flexor areas, they appear throughout the body without preferential flexor involvement, making this statement less accurate than the other options. *Secondary attack rate is 90%* - This statement is **true**. Varicella is highly contagious with an R₀ (basic reproduction number) of 10-12. - The **secondary attack rate** among susceptible household contacts ranges from **80-90%**, making it one of the most contagious viral infections. *Reactivation occurs in 10-30% of cases* - This statement is **true**. After primary varicella infection, varicella-zoster virus (VZV) remains **latent in dorsal root ganglia**. - **Lifetime risk** of reactivation causing **herpes zoster (shingles)** is approximately **10-30%**, increasing with age and immunosuppression.

Question 387: Chance of acquiring Hepatitis B infection by eye splash with Hepatitis B positive patient blood:

A. 10%
B. 0.30% (Correct Answer)
C. 20%
D. 30%

Explanation: ***0.30%*** - The chance of acquiring **Hepatitis B infection** via an **eye splash (mucous membrane exposure)** from HBV-positive blood is approximately **0.3%**. - This risk is significantly lower than that following **percutaneous injury** (e.g., needlestick), which ranges from **6-30%** depending on the viral load and HBeAg status. - **Post-exposure prophylaxis (PEP)** with hepatitis B immunoglobulin (HBIG) and vaccination is recommended following such exposures. *10%* - This risk is **higher than the actual rate** for mucous membrane exposure to HBV. - A 10% transmission risk is closer to the **lower-to-mid range for percutaneous exposure** (needlestick injury), not mucosal exposure. *20%* - This percentage represents a risk **much higher** than that associated with mucous membrane exposure to Hepatitis B contaminated blood. - The 20% mark falls within the **mid-range for percutaneous exposure** from an HBeAg-positive source, not an eye splash. *30%* - This represents the **highest estimated risk** for Hepatitis B transmission through **percutaneous injury** (deep needlestick from HBeAg-positive patient with high viral load). - This is a significant **overestimation for eye splash (mucous membrane exposure)**, which carries approximately 100 times lower risk.

Question 388: According to WHO guidelines, the minimum recommended denier count for polyethylene mosquito nets (LLINs) for effective malaria prevention is:

A. 250 denier
B. 350 denier
C. 100 denier
D. 150 denier (Correct Answer)

Explanation: ***150*** - The World Health Organization (WHO) recommends a minimum of **150 denier polyethylene** or **75 denier polyester** for long-lasting insecticidal nets (LLINs) to ensure durability and effectiveness. - This denier count provides the necessary strength to withstand household conditions and repeated washing over several years without compromising the net's ability to prevent mosquito bites. *250* - While a denier count of **250** would generally indicate a thicker and potentially more durable fabric, it is not the *minimum recommended* by the WHO for effective malaria prevention using LLINs. - Such a high denier count might make the net heavier, more expensive, and potentially reduce breathability without offering significantly greater, WHO-mandated protective benefits over the recommended standard. *350* - A denier count of **350** would result in a very thick and heavy net material, which is well above the minimum recommendation for insecticide-treated nets (ITNs) and long-lasting insecticidal nets (LLINs) by the WHO. - While it would be durable, it is not the **most important characteristic** in terms of meeting the fundamental effectiveness guidelines for malaria prevention and might lead to issues like increased cost, reduced airflow, and user discomfort. *100* - A denier count of **100** (for polyethylene) falls below the WHO's recommended minimum denier for long-lasting insecticidal nets (LLINs). - Nets with a lower denier count are generally **less durable** and more prone to tearing, which can compromise their effectiveness in preventing mosquito bites over their intended lifespan.

Question 389: Hepatitis B infection spreads through all of the following routes except

A. Blood transfusion
B. Sexual contact
C. Perinatal transmission
D. Fecal-oral route (Correct Answer)

Explanation: ***Fecal-oral route*** - **Hepatitis B** is primarily transmitted through contact with infected **blood** or **body fluids**, not via the fecal-oral route. - Diseases spread by the fecal-oral route are typically characterized by poor hygiene and contaminated food or water, which is not the case for Hepatitis B. *Blood transfusion* - Transmission through **blood transfusions** was a significant route before routine screening of blood products for **Hepatitis B surface antigen (HBsAg)** was implemented. - Although rare now in developed countries, it remains a possible route if unscreened blood is used. *Sexual contact* - **Hepatitis B virus (HBV)** is present in **semen** and **vaginal fluids**, making unprotected sexual intercourse a very common mode of transmission. - The risk of transmission increases with the number of partners and certain sexual practices. *Perinatal transmission* - **Perinatal transmission** from an infected mother to her newborn during **childbirth** is a major route of HBV spread, especially in endemic areas. - This can lead to chronic infection in infants if not prevented with immunoprophylaxis.

Question 390: Which one of the following is an emerging viral disease?

A. SARS (Correct Answer)
B. Measles
C. Chicken pox
D. Rabies

Explanation: ***SARS*** - **SARS (Severe Acute Respiratory Syndrome)** emerged in 2002-2003 and caused a global outbreak, making it a classic example of an **emerging viral disease**. - Emerging viral diseases are those that have recently appeared in a population or whose incidence has increased rapidly in recent times. *Measles* - Measles is an **established and re-emerging disease**, meaning it has been present for a long time but has seen resurgence due to factors like declining vaccination rates. - It is caused by the **measles virus (MeV)**, a paramyxovirus, and has been a known human pathogen for centuries. *Chicken pox* - Chickenpox, caused by the **varicella-zoster virus (VZV)**, is a common and well-known childhood disease that has been endemic for a long time. - While it can be severe, it is not considered an emerging disease as its presence and characteristics have been established for many years. *Rabies* - Rabies, caused by the **rabies virus**, is a highly fatal disease primarily transmitted through animal bites and has been recognized globally for centuries. - Although it remains a significant public health concern, it is an **ancient and well-established zoonotic disease**, not an emerging one.

Practice by Chapter

Communicable Disease Control Principles

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Vector-Borne Diseases

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Water-Borne Diseases

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Air-Borne Diseases

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Zoonotic Diseases

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Sexually Transmitted Infections

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HIV/AIDS Control Program

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Tuberculosis Control

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Leprosy Elimination

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Emerging and Re-emerging Infections

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Hospital-Acquired Infections

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Integrated Disease Surveillance Project

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