Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 291: Molar ratio of Sodium and Glucose in WHO ORS is:

A. 1:1 (Correct Answer)
B. 1:2
C. 2:1
D. 1:4

Explanation: ***1:1*** - The **WHO Low-Osmolarity ORS** (recommended since 2002) contains **75 mmol/L of both sodium and glucose**, resulting in a **1:1 molar ratio**. - This formulation is based on the principle of **sodium-glucose co-transport** across the intestinal mucosa, where glucose facilitates sodium absorption, and water follows passively. - The 1:1 ratio in the low-osmolarity formulation (total osmolarity ~245 mOsm/L) has been shown to **reduce stool output by 20%** and **decrease the need for IV therapy by 33%** compared to the older standard ORS. - This is the **current WHO and UNICEF recommendation** for managing acute diarrhea. *1:2* - This ratio is **not used in WHO ORS formulations**. - A higher glucose concentration relative to sodium would create a more **hyperosmolar solution**, potentially worsening osmotic diarrhea. - This does not represent any standard ORS formulation. *2:1* - A 2:1 ratio of sodium to glucose would provide **excessive sodium** relative to glucose. - This would result in a **hypertonic solution** that could draw water into the intestinal lumen, potentially worsening dehydration. - The sodium-glucose co-transport mechanism works optimally when both are present in **balanced proportions**. *1:4* - This ratio implies **excessive glucose** relative to sodium (4 times more glucose than sodium). - High glucose concentration would create significant **osmotic load**, potentially causing osmotic diarrhea. - The **reduced sodium content** would be insufficient for effective rehydration and electrolyte replacement in diarrheal diseases.

Question 292: In which of the following situations is rabies vaccination generally NOT indicated?

A. Cat bite
B. Rat bite (Correct Answer)
C. Monkey bite
D. Dog bite

Explanation: ***Rat bite*** - Rabies vaccination is generally **not indicated** for rat bites because rodents (like rats, mice, hamsters, guinea pigs) are **rarely** infected with rabies and are not known to transmit the disease to humans. - The **Centers for Disease Control and Prevention (CDC)** guidelines typically advise against post-exposure prophylaxis for rodent bites unless there's an unusual epidemiological circumstance. *Cat bite* - Cat bites are a significant concern for rabies transmission, especially if the cat is **feral**, unvaccinated, or its health status is unknown. - **Post-exposure prophylaxis** is often recommended following a cat bite, particularly if the animal cannot be observed or tested. *Monkey bite* - Monkey bites pose a risk for rabies transmission, especially in regions where rabies is **endemic** among wildlife and other animals. - Monkeys can carry and transmit the virus, and their bites often warrant **rabies prophylaxis**. *Dog bite* - Dog bites are a common reason for rabies vaccination, particularly in areas where rabies is **prevalent** among dog populations. - If the dog is **unvaccinated**, strays, or its vaccination status is unknown, **post-exposure prophylaxis** is usually indicated.

Question 293: Most common organism that can contaminate crowded army camps is?

A. Neisseria meningitidis (Correct Answer)
B. Klebsiella
C. Staphylococcus
D. E. coli

Explanation: ***Neisseria meningitidis*** - This bacterium is a common cause of **meningitis** and can spread rapidly in crowded environments like army camps due to close contact. - Transmission occurs through **respiratory droplets**, making confined spaces ideal for its dissemination. *Klebsiella* - While *Klebsiella* can cause various infections, including pneumonia and UTIs, it is not typically associated with widespread outbreaks in crowded settings like meningococcal disease. - It usually acts as an **opportunistic pathogen**, often affecting individuals with weakened immune systems or those in healthcare settings. *Staphylococcus* - *Staphylococcus* species, particularly *S. aureus*, are common causes of skin infections, bloodstream infections, and food poisoning. - However, they are not the most frequent cause of highly transmissible, community-wide outbreaks in crowded camps, unlike meningococcus. *E. coli* - *E. coli* is a common cause of **urinary tract infections** and **gastroenteritis**, often associated with contaminated food or water. - It is not typically responsible for widespread respiratory outbreaks in crowded, healthy populations like *Neisseria meningitidis*.

Question 294: Transmission assessment survey (TAS) is done for which of the following purposes?

A. To provide reliable estimates of birth rate, death rate and infant mortality rate
B. For assessing primary immunization coverage
C. All of the options
D. To determine when infections have been reduced below target transmission thresholds (Correct Answer)

Explanation: ***To determine when infections have been reduced below these target thresholds*** - **Transmission assessment surveys (TAS)** are specifically designed to evaluate if the prevalence of a **neglected tropical disease (NTD)**, such as **lymphatic filariasis** or **trachoma**, has fallen below a critical threshold. - This assessment is crucial for determining whether to **stop mass drug administration (MDA)** campaigns and move towards post-MDA surveillance. *To provide reliable estimates of birth rate, death rate and infant mortality rate* - This function is typically associated with **demographic and health surveys (DHS)** or national vital statistics registration systems, not TAS. - These surveys focus on population-level health indicators and cannot determine infectious disease transmission levels. *For assessing primary immunization coverage* - Immunization coverage is assessed through specific **immunization coverage surveys (ICS)** or analysis of routine administrative data. - TAS is designed for infectious disease transmission, not vaccine uptake. *All of the options* - Only the first option accurately describes the specific purpose of a **Transmission Assessment Survey (TAS)**. - The other options relate to different types of public health surveys with distinct objectives.

Question 295: Disinfection of urine is which type of disinfection ?

A. Concurrent (Correct Answer)
B. Terminal
C. Preconcurrent
D. Precurrent

Explanation: ***Concurrent*** - **Concurrent disinfection** refers to the immediate disinfection of infectious materials and objects **as soon as they are discharged** from the body of an infected person. - Disinfection of **body excretions** (urine, feces, sputum) and articles contaminated by them is done **promptly after they are voided**, making it concurrent disinfection. - In the context of urine from infected patients, it should be disinfected **immediately after collection** to prevent spread of infection. *Terminal* - **Terminal disinfection** is performed **after the patient has been discharged, died, or is no longer infectious**. - It involves thorough cleaning and disinfection of the **room, furniture, and environment** that the patient occupied. - Terminal disinfection is not the routine disinfection of body excretions, but rather the final cleaning of the patient's surroundings. *Preconcurrent* - **"Preconcurrent"** is not a standard or recognized term in the classification of disinfection types. - This option does not describe a method or timing of disinfection that is medically or scientifically established. *Precurrent* - Similar to "preconcurrent," **"precurrent"** is not a recognized category or term used to describe a type of disinfection process. - The standard classifications include **concurrent, terminal, and prophylactic disinfection**.

Question 296: Most sensitive index of transmission in leprosy is -

A. Disability rate
B. Incidence (Correct Answer)
C. Prevalence
D. Detection rate

Explanation: ***Incidence*** - **Incidence rate** measures the number of **new cases** of a disease in a population over a specific period, directly reflecting the rate of disease transmission. - A higher incidence suggests more active transmission of *Mycobacterium leprae* within the community. *Disability rate* - The **disability rate** reflects the long-term consequences and severity of the disease, not its current transmission dynamics. - It indicates the burden of disease over time, but not the rate at which new infections are occurring. *Prevalence* - **Prevalence** measures the total number of **existing cases** (new and old) in a population at a given time or over a period. - While it shows the overall burden, it doesn't specifically indicate the rate of new infections or recent transmission. *Detection rate* - The **detection rate** refers to the number of cases diagnosed, which is influenced by surveillance and healthcare access. - It can be an indicator of case finding efforts rather than the true transmission rate, as undetected cases are not accounted for.

Question 297: Most important disease transmitted by louse -?

A. Q fever
B. Trench fever
C. Scrub Typhus
D. Epidemic typhus (Correct Answer)

Explanation: ***Epidemic typhus*** - **Epidemic typhus** is caused by **Rickettsia prowazekii** and is primarily transmitted by the **human body louse** (*Pediculus humanus corporis*). - It is one of the most significant louse-borne diseases, causing severe illness and high mortality in conditions of overcrowding and poor hygiene. *Q fever* - **Q fever** is caused by **Coxiella burnetii** and is primarily transmitted through inhalation of aerosols from infected animals, such as livestock. - It is **not transmitted by lice**; rather, it is an occupational hazard for individuals working with animals. *Trench fever* - **Trench fever** is caused by **Bartonella quintana** and is transmitted by the **human body louse**. - While louse-borne, it is generally considered less severe and fatal than epidemic typhus, though it was a significant problem during the world wars. *Scrub Typhus* - **Scrub typhus** is caused by **Orientia tsutsugamushi** and is transmitted by the bites of infected **chigger mites (larval trombiculid mites)**. - It is **not transmitted by lice**, and its geographical distribution and vector are distinct from louse-borne illnesses.

Question 298: What is the ideal mesh opening size for an effective mosquito net according to WHO standards?

A. 0.5 mm mesh opening
B. 1.2-1.7 mm mesh opening (Correct Answer)
C. 3.0 mm mesh opening
D. 2.5 mm mesh opening

Explanation: ***1.2-1.7 mm mesh opening*** - The **World Health Organization (WHO)** recommends a mesh size of **1.2-1.5 mm (approximately 156 holes per square inch)** as the standard for effective mosquito nets. - This mesh opening size provides the **ideal balance** between blocking mosquito entry and maintaining adequate ventilation for comfortable sleeping. - It effectively prevents entry of **Anopheles** and **Culex** mosquitoes, the primary vectors for malaria and other mosquito-borne diseases, while allowing sufficient airflow. *2.5 mm mesh opening* - A mesh opening of **2.5 mm is too large** and would allow smaller mosquito species to pass through, particularly young adult mosquitoes. - This would **significantly reduce the protective efficacy** of the net against mosquito-borne diseases like malaria, dengue, and filariasis. - Such large mesh openings fail to meet WHO standards for insecticide-treated nets (ITNs) and long-lasting insecticidal nets (LLINs). *0.5 mm mesh opening* - This mesh size would be **unnecessarily fine** and would significantly restrict airflow, creating a hot and uncomfortable sleeping environment. - The **reduced ventilation** would decrease user compliance and acceptance, undermining the public health benefit. - It is not required for blocking standard mosquito species and would increase manufacturing costs without additional benefit. *3.0 mm mesh opening* - A mesh opening of **3.0 mm is far too large** to provide adequate protection against mosquitoes. - This would allow **easy passage of most mosquito species**, rendering the net essentially ineffective as a barrier. - Such nets would not meet any international standards for vector control and disease prevention.

Question 299: In which body site do health workers commonly carry microbes causing healthcare-associated infections (haemolytic Streptococcus)?

A. Nail
B. Skin
C. Hair
D. Throat (Correct Answer)

Explanation: ***Throat*** - The **throat** (pharynx) is a common colonization site for **Streptococcus pyogenes** (Group A Streptococcus), often considered a **hospital-acquired infection** risk if transmitted. - Asymptomatic carriers can harbor these bacteria in their throat, potentially transmitting them to vulnerable patients. *Nail* - While bacteria can accumulate under fingernails, they are not typically a primary or significant reservoir for **haemolytic Streptococcus** colonization in healthcare workers. - Proper hand hygiene, including nail cleaning, is crucial but does not address nasal or throat carriage. *Skin* - The skin can harbor various microbes, but **haemolytic Streptococcus** (like *S. pyogenes*) is more commonly found colonizing mucosal surfaces such as the **throat** rather than being a primary skin colonizer. - Skin colonization with other bacteria, such as *Staphylococcus aureus*, is more common and contributes to healthcare-associated infections. *Hair* - Hair itself is not a significant site for the long-term colonization of **haemolytic Streptococcus**. - While hair can temporarily harbor microorganisms from the environment, it does not serve as a primary reservoir for these pathogens.

Question 300: Which of the following is the most defining characteristic of Kyasanur Forest disease (KFD)?

A. Affects monkeys
B. Caused by rickettsia
C. Caused by bacteria
D. It is zoonosis (Correct Answer)

Explanation: ***It is zoonosis*** - **Kyasanur Forest disease (KFD)** is primarily a **zoonotic disease**, meaning it is transmitted from animals to humans. - The disease cycle involves forest animals, particularly **monkeys**, and is transmitted to humans through the bite of infected ticks. *Affects monkeys* - While **monkeys** are indeed affected by KFD and serve as an important amplifying host, this is a part of its zoonotic nature rather than the most defining characteristic itself. - The disease is devastating for monkey populations, but the broader concept of **zoonosis** more accurately defines its transmission to humans. *Caused by rickettsia* - KFD is caused by the **Kyasanur Forest disease virus (KFDV)**, which is a **flavivirus**, not a rickettsial organism. - **Rickettsial diseases** are caused by bacteria, and they are distinct from viral infections like KFD. *Caused by bacteria* - **Kyasanur Forest disease** is caused by a **virus (KFDV)**, belonging to the Flaviviridae family, not by bacteria. - Bacterial diseases and viral diseases have different etiologies, treatments, and often different clinical presentations.

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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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