Infectious Diseases Practice Questions

Q: Contact isolation is done for

MRSA. ***MRSA*** - **Methicillin-resistant *Staphylococcus aureus* (MRSA)** is transmitted primarily through direct contact with infected patients or contaminated surfaces, necessitating **contact isolation**. - **Contact precautions** involve the use of **gloves** and **gowns** when entering the patient's room to prevent transmission. *Mumps* - Mumps is a viral infection that is primarily transmitted via **respiratory droplets** produced during coughing, sneezing, or talking. - Patients with mumps typically require **droplet isolation**, not contact isolation, to prevent airborne transmission. *Diphtheria* - Diphtheria is a bacterial infection spread through **respiratory droplets** from the nose and throat of an infected person. - **Droplet precautions** are generally recommended for diphtheria, involving masks within a certain distance, rather than contact isolation. *Asthma* - **Asthma** is a chronic inflammatory condition of the airways and is not an infectious disease. - As asthma is not transmissible, it does **not require any form of isolation precautions** (contact, droplet, or airborne).

Q: Which of the following is an example of indirect transmission by a living vector?

Transmission by mosquito. ***Transmission by mosquito*** - This is the classic example of **vector-borne transmission**, where a living biological vector (the mosquito) acts as an intermediary to transmit the infectious agent from an infected host to a susceptible one. - The disease-causing microorganism does not pass directly from person to person but is carried and transmitted by the living vector. - Examples include malaria, dengue, and filariasis. *Vertical transmission* - This refers to transmission of disease from a **mother to her child** during pregnancy, childbirth, or breastfeeding. - This is a form of **direct transmission** where the pathogen passes directly between biologically related individuals without an intermediate living vector. *Soil contact* - This represents **vehicle-borne transmission** where soil acts as a non-living vehicle (fomite) carrying pathogens. - While this is technically indirect transmission, it does not involve a **living biological vector** as specified in the question. - Examples include tetanus, hookworm, and ascariasis transmitted through contaminated soil. *Droplet infection* - This is a form of **direct transmission** where infectious droplets are expelled from the respiratory tract of an infected person and directly contact the mucous membranes of a susceptible person. - The droplets travel a short distance in close proximity, representing direct person-to-person transfer without any intermediate vector.

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

Secondary attack rate (SAR) is approximately 90%. ***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.

Q: In the context of malaria control, when is regular insecticidal spray recommended based on the Annual Parasite Index (API)?

> 2. ***> 2*** - Regular insecticidal spray, particularly **Indoor Residual Spraying (IRS)**, is a key malaria control measure recommended when the **Annual Parasite Index (API) is greater than 2**. - An API greater than 2 indicates **high endemicity** with a significant burden of malaria transmission in the community, necessitating aggressive vector control strategies. - According to **NVBDCP (National Vector Borne Disease Control Programme) guidelines**, API > 2 defines high-risk areas where routine IRS is implemented as a core intervention. *> 1* - An API between 1-2 represents **moderate endemicity**, where the focus is primarily on **active case detection, prompt treatment, and targeted interventions** rather than universal spraying. - While vector control remains important, routine widespread IRS is not the standard recommendation at this threshold. *< 2* - An API of less than 2 (which includes both moderate and low endemic areas) does not routinely warrant universal insecticidal spraying programs. - In areas with API < 2, **case management, surveillance, and selective vector control** are prioritized over widespread IRS campaigns. *< 1* - An API of less than 1 indicates **low endemicity**, where malaria transmission is minimal and sporadic. - In such areas, **surveillance, prompt case detection and treatment, and targeted interventions** are the mainstay, with IRS reserved only for focal outbreaks or high-risk pockets.

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

Direct contact. **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.

Q: What is the most common mode of transmission of HIV?

Sexual contact. ***Sexual contact*** - **Unprotected sexual intercourse**, both heterosexual and homosexual, is overwhelmingly the most common way HIV is transmitted globally. - The virus can be exchanged through **bodily fluids** such as semen, vaginal fluids, and rectal fluids during sexual activity. - Accounts for approximately **80% of new HIV infections** worldwide. *Occupational exposure (needle stick injury)* - While a recognised mode of transmission, **needle stick injuries** account for a very small percentage of total HIV infections, primarily affecting healthcare workers. - The risk of transmission per exposure is relatively low (approximately **0.3%**), especially compared to sexual contact. *Perinatal transmission (mother to child)* - **Mother-to-child transmission** can occur during pregnancy, childbirth, or breastfeeding. - Although significant, especially in resource-limited settings, global efforts and **PMTCT programs** have resulted in a significant reduction in this type of transmission. *Transmission via blood and blood products* - This mode was once a major concern but is now extremely rare in countries with robust **blood screening programs**. - While sharing contaminated needles among **intravenous drug users** remains a risk, transfusion-related HIV is largely controlled.

Q: Which of the following is not a recognized transmission route for amoebiasis?

Vector transmission. ***Vector transmission*** - Amoebiasis, caused by *Entamoeba histolytica*, is primarily an **intestinal infection** transmitted through the **fecal-oral route**. - Its life cycle **does not involve any arthropod vector** (e.g., mosquito, tick, fly) for transmission. - This is the **only route among the options that is definitively NOT recognized** for amoebiasis transmission. *Sexual transmission* - Amoebiasis **can be transmitted** through **oral-anal sexual contact**, particularly documented in men who have sex with men (MSM). - This represents an **indirect fecal-oral transmission** route and is a recognized mode of spread. *Blood and blood products* - While *E. histolytica* can disseminate to cause **amoebic liver abscesses** and rarely systemic disease, transmission via blood transfusion is **extremely rare and not well-documented**. - However, theoretically possible in cases of parasitemia during invasive disease. - Unlike vector transmission, this cannot be definitively ruled out as "not recognized." *Fecal-oral route* - This is the **primary and most important transmission route** for amoebiasis. - Infection occurs through ingestion of **cysts** from contaminated food, water, or through direct person-to-person contact with poor hand hygiene.

Q: Droplet nuclei is a type of ?

Indirect transmission of pathogens. ***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.

Q: Reservoir of infection in enteric fever?

Man. ***Man*** - Humans are the **sole natural reservoir** for *Salmonella Typhi* and *Salmonella Paratyphi*, the causative agents of enteric fever (typhoid and paratyphoid fever). - The bacteria can persist in the **gallbladder** of asymptomatic carriers, who can then shed the bacteria in their feces, contributing to transmission. *Birds* - Birds are not considered a primary reservoir for the **causative pathogens of enteric fever** (*Salmonella Typhi* or *Paratyphi*). - They are more commonly associated with other *Salmonella* serotypes, such as *Salmonella Enteritidis*, which cause **gastroenteritis** rather than systemic enteric fever. *Cow* - Cows are not a primary reservoir for the organisms responsible for **enteric fever**; these pathogens are specifically adapted to humans. - While cows can carry various *Salmonella* species, they are typically associated with **foodborne outbreaks** of *Salmonella*-induced **gastroenteritis**, not typhoid fever. *Water* - Water is a **vehicle for transmission** of enteric fever, becoming contaminated with human feces containing *Salmonella Typhi* or *Paratyphi*. - It is not a reservoir because the bacteria do not naturally **multiply or persist indefinitely** in water without a human source.

Question 1

Contact isolation is done for

Accepted Answer

MRSA

Answer

Mumps

Answer

Asthma

Answer

Diphtheria

Question 2

Which of the following is an example of indirect transmission by a living vector?

Accepted Answer

Transmission by mosquito

Answer

Vertical transmission

Answer

Soil contact

Answer

Droplet infection

Question 3

Which of the following is the most epidemiologically distinctive feature of chickenpox?

Accepted Answer

Secondary attack rate (SAR) is approximately 90%

Answer

Caused by varicella-zoster virus

Answer

Most commonly affects children under 10 years old

Answer

Infectious period is 1-2 days before rash until all blisters have scabbed over

Question 4

In the context of malaria control, when is regular insecticidal spray recommended based on the Annual Parasite Index (API)?

Accepted Answer

> 2

Answer

< 1

Answer

< 2

Answer

> 1

Question 5

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

Accepted Answer

Direct contact

Answer

Droplet transmission

Answer

Indirect contact

Answer

Vehicle transmission

Question 6

What is the most common mode of transmission of HIV?

Accepted Answer

Sexual contact

Answer

Occupational exposure (needle stick injury)

Answer

Perinatal transmission (mother to child)

Answer

Transmission via blood and blood products

Question 7

Which of the following is not a recognized transmission route for amoebiasis?

Accepted Answer

Vector transmission

Answer

Sexual transmission

Answer

Blood and blood products

Answer

Fecal-oral route

Question 8

Droplet nuclei is a type of ?

Accepted Answer

Indirect transmission of pathogens

Answer

Direct transmission of infectious agents

Answer

Vertical transmission of pathogens

Answer

Biological transmission of pathogens

Question 9

Reservoir of infection in enteric fever?

Accepted Answer

Man

Answer

Birds

Answer

Cow

Answer

Water

Question 10

What is the definition of a reservoir in the context of infectious diseases?

Accepted Answer

Person, animal or substance in which infectious agent lives and multiplies

Answer

Person, animal or object from which infectious agent is transmitted to host

Answer

Person or animal in which infectious agent causes a disease

Answer

Person or animal that transmits the infectious agent mechanically

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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