Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 621: Which of the following statements about universal precautions is false?

A. Includes use of hand washing
B. Consider that all body fluids are contaminated with blood (Correct Answer)
C. Includes use of gloves and masks
D. To prevent transmission of blood borne pathogens

Explanation: ***Correct: Consider that all body fluids are contaminated with blood*** - This statement is **FALSE** and therefore the correct answer to this question asking what is false about universal precautions. - **Universal precautions** do NOT assume all body fluids are "contaminated with blood." Instead, they specify that **certain body fluids** (blood, semen, vaginal secretions, cerebrospinal fluid, synovial fluid, pleural fluid, peritoneal fluid, pericardial fluid, amniotic fluid, and any body fluid visibly contaminated with blood) should be treated as **potentially infectious for bloodborne pathogens** (HIV, HBV, HCV). - The distinction is important: it's about **potential infectivity for bloodborne pathogens**, not that all body fluids are literally contaminated with blood. Universal precautions do NOT apply to feces, nasal secretions, saliva, sputum, sweat, tears, urine, or vomitus unless they contain visible blood. *Incorrect: Includes use of hand washing* - This statement is **TRUE** about universal precautions (therefore incorrect as an answer to what is false). - **Hand hygiene** is a **fundamental component** of universal and standard precautions, essential for preventing transmission of microorganisms between patients and healthcare workers. *Incorrect: Includes use of gloves and masks* - This statement is **TRUE** about universal precautions (therefore incorrect as an answer to what is false). - **Personal protective equipment (PPE)** including gloves, masks, gowns, and eye protection are **integral to universal precautions**. - Gloves are used when contact with blood or specified body fluids is anticipated; masks and eye protection are used during procedures likely to generate splashes or sprays. *Incorrect: To prevent transmission of blood borne pathogens* - This statement is **TRUE** about universal precautions (therefore incorrect as an answer to what is false). - The **primary goal** of universal precautions is to **prevent transmission of bloodborne pathogens** such as HIV, Hepatitis B (HBV), and Hepatitis C (HCV) by creating barriers between healthcare workers and potentially infectious materials.

Question 622: Most common route of nosocomial infection [Hospital-acquired infection]?

A. Droplet transmission
B. Direct contact (Correct Answer)
C. Indirect contact
D. Vehicle transmission

Explanation: **Direct contact** - **Direct contact** with colonized or infected patients is the predominant mode of transmission for many common nosocomial pathogens like **MRSA** and **VRE**. - This often involves healthcare workers' hands becoming contaminated and then touching other patients. *Droplet transmission* - Involves the transmission of infectious agents through **respiratory droplets** produced during coughing, sneezing, or talking. - While significant for some infections (e.g., influenza, pertussis), it is not the most common route overall for nosocomial infections. *Indirect contact* - Occurs when an infectious agent is transferred via a **contaminated intermediate object** or person. - Although important (e.g., contaminated medical devices), it is generally less frequent than direct patient-to-patient transmission. *Vehicle transmission* - Involves transmission through **contaminated inanimate vehicles** like food, water, medications, or surgical instruments. - While outbreaks can occur via this route (e.g., contaminated endoscopes), it is not the most common day-to-day transmission mechanism in hospitals.

Question 623: Which of the following statements about pathogenic mosquitoes is correct?

A. Mansonia mosquitoes lay their eggs in rafts.
B. Culex mosquitoes are primarily vectors for West Nile virus.
C. Aedes mosquitoes are known for their distinctive black and white striped markings.
D. Anopheles mosquitoes are known for transmitting malaria. (Correct Answer)

Explanation: ***Correct: Anopheles mosquitoes are known for transmitting malaria.*** - **Anopheles mosquitoes** are the **primary and only vectors** for **malaria**, a parasitic disease caused by Plasmodium parasites. - They transmit the parasite through their **saliva** when they bite humans, typically during **dusk and dawn**. - This is the most significant pathogenic association among the options. *Incorrect: Mansonia mosquitoes lay their eggs in rafts.* - **Mansonia mosquitoes** lay their eggs in **clusters attached to underwater parts of aquatic plants**, not in rafts. - **Culex mosquitoes** are the ones that lay their eggs in **raft-like formations** on water surfaces. *Incorrect: Culex mosquitoes are primarily vectors for West Nile virus.* - While **Culex mosquitoes** can transmit West Nile virus, in the **Indian context** they are primarily known as vectors for **lymphatic filariasis** (Wuchereria bancrofti) and **Japanese encephalitis**. - West Nile virus is more relevant in Western countries and is not the primary disease association for Culex in India. *Incorrect: Aedes mosquitoes are known for their distinctive black and white striped markings.* - While **Aedes aegypti** and **Aedes albopictus** do have **black and white striped markings**, this is a **morphological characteristic** rather than a primary **pathogenic association**. - The question asks about pathogenic mosquitoes, and Aedes is better characterized by its **disease transmission** (dengue, Zika, chikungunya, yellow fever) rather than its appearance. - As a pathogenic mosquito, its **daytime biting behavior** and **urban breeding habits** are more relevant than its markings.

Question 624: Drug of choice for mass therapy under filariasis control programme?

A. Albendazole
B. Ivermectin
C. DEC (Correct Answer)
D. Mebendazole

Explanation: ***Correct: DEC*** - **Diethylcarbamazine (DEC)** is the drug of choice for **mass drug administration (MDA)** campaigns aimed at eliminating lymphatic filariasis. - It effectively kills **microfilariae** and has some action on adult worms, reducing transmission. - In India's National Filariasis Elimination Programme, DEC is administered along with Albendazole in annual MDA campaigns. *Incorrect: Albendazole* - While **Albendazole** is co-administered with DEC in MDA programs, it is not the sole drug of choice for mass treatment of filariasis. - Its primary role is to provide **macrofilaricidal** activity (killing adult worms) and co-treatment for other helminth infections. - It enhances the effect of DEC but is not used alone. *Incorrect: Ivermectin* - **Ivermectin** is used in MDA programs for filariasis, particularly in areas co-endemic with **onchocerciasis** or where **Loa loa** is prevalent (as DEC is contraindicated in these areas). - However, in India and most lymphatic filariasis endemic areas, **DEC** remains the primary drug. *Incorrect: Mebendazole* - **Mebendazole** is an anthelminthic primarily used for treating **intestinal nematode infections** like ascariasis, trichuriasis, and hookworm. - It is **not used** in lymphatic filariasis mass treatment programs.

Question 625: Droplet nuclei is a type of ?

A. Direct transmission of infectious agents
B. Vertical transmission of pathogens
C. Biological transmission of pathogens
D. Indirect transmission of pathogens (Correct Answer)

Explanation: ***Indirect transmission of pathogens*** - **Droplet nuclei** are tiny airborne particles remaining after the evaporation of respiratory droplets, suspended in the air for prolonged periods, allowing pathogens to travel over longer distances. - This mode of transmission is considered **indirect** because it involves an environmental medium (air) rather than direct contact between individuals. *Vertical transmission of pathogens* - This refers to the transmission of a pathogen from a **mother to her offspring**, either during pregnancy, childbirth, or breastfeeding. - Examples include HIV and rubella, which are transmitted directly from parent to child, unlike airborne droplet nuclei. *Direct transmission of infectious agents* - This involves immediate physical contact or exposure between an infected individual and a susceptible host (e.g., touching, kissing, sexual contact). - It does not involve an intermediate environmental vehicle such as airborne particles that travel through the air from their source. *Biological transmission of pathogens* - This type of transmission involves an **arthropod vector** that not only transmits the pathogen but also allows it to multiply or develop within its body before transmission. - Examples include malaria transmitted by mosquitoes or Lyme disease by ticks, which is distinct from airborne droplet nuclei transmission.

Question 626: Under NTEP, what is the honorarium given to a DOTS provider after the completion of treatment?

A. 150 INR
B. 500 INR (Correct Answer)
C. 1000 INR
D. 250 INR

Explanation: ***500 INR*** - Under the **National Tuberculosis Elimination Programme (NTEP)**, a **DOTS provider** receives an honorarium of **INR 500** upon the successful completion of tuberculosis treatment for a **new TB patient**. - This incentive, revised from the earlier amount of INR 250, aims to recognize the crucial role of DOTS providers in ensuring treatment adherence and successful outcomes. - The increased honorarium reflects the government's commitment to incentivizing community participation in TB elimination. *150 INR* - This amount is **significantly lower than the stipulated honorarium** for a DOTS provider upon treatment completion under current NTEP guidelines. - The correct incentive for successful completion of treatment is INR 500 for new TB cases. *250 INR* - This was the **earlier honorarium amount** under the previous NTEP guidelines, which has since been **revised upward**. - Under the current NTEP incentive structure, the honorarium for treatment completion has been increased to INR 500. *1000 INR* - This amount is **higher than the designated honorarium** for a DOTS provider upon treatment completion under NTEP. - While this figure may apply to other incentive schemes or different milestones, the standard honorarium for new TB case completion is INR 500.

Question 627: Which of the following is the most epidemiologically distinctive feature of chickenpox?

A. Caused by varicella-zoster virus
B. Most commonly affects children under 10 years old
C. Secondary attack rate (SAR) is approximately 90% (Correct Answer)
D. Infectious period is 1-2 days before rash until all blisters have scabbed over

Explanation: ***Secondary attack rate (SAR) is approximately 90%*** - A **secondary attack rate (SAR)** of around 90% is exceptionally high, indicating that chickenpox is one of the most **contagious infectious diseases**, readily spreading among susceptible household contacts. - This high SAR highlights the disease's **distinctive epidemiological characteristic** of efficient person-to-person transmission within close-contact settings. *Caused by varicella-zoster virus* - While true, many diseases are caused by specific viruses, and this fact alone is not an **epidemiologically distinctive feature** in terms of transmissibility or population impact. - The causative agent defines the disease, but doesn't uniquely describe its spread or contagiousness in an epidemiological sense. *Most commonly affects children under 10 years old* - Many common childhood infections, such as measles or mumps, also primarily affect children, making this less of a **distinctive epidemiological feature** for chickenpox specifically. - The age group affected is common for many highly transmissible diseases of childhood. *Infectious period is 1-2 days before rash until all blisters have scabbed over* - Many infectious diseases have similar **infectious periods** spanning from a prodromal phase to resolution, making this a general feature of viral infections rather than one highly distinctive to chickenpox epidemiologically. - While important for infection control, it doesn't stand out as uniquely characteristic of chickenpox's epidemiological profile compared to other common infectious diseases.

Question 628: Which of the following statements about influenza infectivity is correct?

A. Communicable period is 1 day before to 5-7 days after the onset of symptoms
B. All of the options are correct. (Correct Answer)
C. There can be subclinical cases of influenza.
D. The primary source of infection is a clinical case.

Explanation: ***All of the options are correct.*** - All statements provided accurately describe aspects of influenza infectivity and epidemiology. - The **communicable period**, the **primary source of infection**, and the potential for **subclinical cases** are all characteristic features of influenza. *Communicable period is 1 day before to 5-7 days after the onset of symptoms* - This statement is accurate, as influenza is transmissible **before symptom onset** and for several days afterward, which contributes to its rapid spread. - Peak viral shedding often occurs just before and in the first few days of symptomatic illness. - Adults typically shed virus from 1 day before to 5-7 days after symptom onset (can be longer in children and immunocompromised individuals). *The primary source of infection is a clinical case.* - This is correct, as **symptomatic individuals (clinical cases) are the PRIMARY source** of influenza virus transmission to others. - Respiratory droplets produced by coughing, sneezing, or talking from an infected person are the main mode of spread. - While subclinical cases can transmit, clinical cases with overt symptoms produce more respiratory droplets and are the major drivers of transmission. *There can be subclinical cases of influenza.* - This statement is correct; many individuals infected with influenza virus experience **mild or asymptomatic infections** (subclinical cases). - These subclinical cases can still transmit the virus, though typically to a lesser extent than symptomatic cases, further complicating control efforts.

Question 629: Pneumonic plague is spread by:

A. Direct contact with infected tissue
B. Bite of infected flea
C. Ingestion of contaminated food
D. Droplet infection (Correct Answer)

Explanation: ***Correct: Droplet infection*** - Pneumonic plague is a severe form of plague that affects the **lungs** and is transmitted through **respiratory droplets** expelled by an infected person or animal during coughing or sneezing. - This direct person-to-person transmission distinguishes it from other forms of plague. - It is the **only form of plague** that can spread directly from human to human without an animal or flea vector. *Incorrect: Bite of infected flea* - This is the primary mode of transmission for **bubonic plague**, where the bacterium *Yersinia pestis* is transmitted from rodents to humans via infected fleas. - While bubonic plague can progress to pneumonic plague, the initial transmission route for the pneumonic form itself is not flea bites. *Incorrect: Direct contact with infected tissue* - Direct contact with infected tissues or fluids can lead to **septicemic plague** or sometimes bubonic plague, especially in cases where there is a break in the skin. - This is not the typical or primary route for the spread of pneumonic plague, which is respiratory. *Incorrect: Ingestion of contaminated food* - Ingestion of contaminated food or water is a route for various **gastrointestinal infections** and diseases like salmonella or cholera. - It is not a known or common method for the transmission of any form of plague, including pneumonic plague.

Question 630: What is the most appropriate method for disinfecting urine specimens in clinical settings?

A. UV disinfection
B. Heat sterilization
C. Standard precautions (Correct Answer)
D. Chemical disinfection

Explanation: ***Standard precautions*** - **Standard precautions** are the appropriate method for handling urine specimens in clinical settings, treating all biological specimens as potentially infectious. - This includes use of **personal protective equipment (PPE)**, proper containment in leak-proof containers, and safe handling practices to protect laboratory personnel. - Importantly, the specimen itself is **NOT disinfected** before analysis, as this would destroy pathogens, cells, and other diagnostic elements that need to be identified. - Standard precautions prevent exposure while maintaining **specimen integrity** for accurate diagnostic testing including culture, microscopy, and biochemical analysis. *UV disinfection* - UV light would **kill bacteria** needed for urine culture and sensitivity testing, rendering the specimen useless for microbiological diagnosis. - It would also damage **cellular elements** (WBCs, RBCs, epithelial cells) required for microscopic examination. - UV disinfection has **no role** in routine clinical urine specimen processing for diagnostic purposes. *Chemical disinfection* - Chemical disinfectants would **destroy pathogens** that need to be isolated and identified in urine culture. - They would interfere with **all subsequent analyses** including biochemical tests, microscopy, and culture. - This method is inappropriate for specimens requiring diagnostic evaluation. *Heat sterilization* - Autoclaving would completely **destroy all diagnostic elements** including bacteria, cells, proteins, and other analytes. - Heat sterilization is used only for **disposal of biohazardous waste** after testing is complete, never for specimen preparation.

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