Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 321: The most effective method of reduction of incidence of institutional pediatric Staphylococcus aureus infection is:

A. Routine isolation of culture positive
B. Meticulous handwashing before and after contact with patients (Correct Answer)
C. Mask and gloves use with each suspected patient
D. Treatment of all culture positive patients with vancomycin

Explanation: **Meticulous handwashing before and after contact with patients** - **Hand hygiene** is the single most effective measure to prevent healthcare-associated infections, including those caused by *Staphylococcus aureus*, by interrupting the transmission of microorganisms. - Regular and thorough **handwashing** with soap and water or alcohol-based hand rub significantly reduces the bacterial load on healthcare workers' hands. *Routine isolation of culture Positive* - While **isolation** can be helpful for specific highly transmissible pathogens, routine isolation of all *S. aureus* culture-positive patients is not practical or the most effective primary strategy for overall incidence reduction. - This approach is resource-intensive and may not prevent transmission from colonized but asymptomatic individuals or those not yet culture-positive. *Mask and gloves use with each suspected patient* - Wearing **masks and gloves** is important for contact and droplet precautions, particularly when direct contact with body fluids or mucous membranes is anticipated. - However, relying solely on gloves and masks without meticulous hand hygiene can lead to contamination if gloves are not changed regularly or hands are not washed after glove removal. *Treatment of all culture Positive patients with vancomycin* - **Empiric vancomycin treatment** of all culture-positive patients is an inappropriate and harmful strategy. - This would contribute significantly to **antibiotic resistance**, as *Staphylococcus aureus* can develop resistance to vancomycin, and it also exposes patients to unnecessary side effects.

Question 322: All are true about communicability of Malaria, except-

A. Gametocytes appear in blood 4-5 days after the appearance of the asexual parasite, in vivax infection.
B. In the early stage of infection, their density may exceed 1000 per cmm of blood.
C. The number of gametocytes in blood increases with time (Correct Answer)
D. Gametocytes appear in blood 10-12 days after the appearance of asexual parasite, in falciparum infection.

Explanation: ***The number of gametocytes in blood increases with time*** - This statement is incorrect because the **density of gametocytes typically decreases** after reaching an early peak, especially as the host's immune response develops. - While gametocytes are essential for transmission, their numbers don't continuously increase; rather, they are produced for a period and then clear, unless chronic infection or re-infection occurs. *Gametocytes appear in blood 4-5 days after the appearance of the asexual parasite, in vivax infection.* - This statement is correct. In **_Plasmodium vivax_ infections**, gametocytes mature relatively quickly, becoming detectable in the bloodstream within a few days of asexual parasite appearance. - This rapid development contributes to the early transmissibility of *P. vivax*. *In the early stage of infection, their density may exceed 1000 per cmm of blood.* - This statement is correct. Particularly in **hyperparasitemic infections** with species like *P. falciparum* or *P. vivax*, high densities of gametocytes can be observed in the early stages, making the individual highly infectious to mosquitoes. - A high gametocyte density significantly increases the probability of transmission to a feeding mosquito. *Gametocytes appear in blood 10-12 days after the appearance of asexual parasite, in falciparum infection.* - This statement is correct. **_Plasmodium falciparum_ gametocytes** take longer to mature and become detectable in the peripheral blood compared to *P. vivax*. - This delayed appearance of *P. falciparum* gametocytes means that individuals may be symptomatic and treated for asexual parasites before becoming fully infectious to mosquitoes.

Question 323: The SAFE strategy is used for elimination of?

A. Bacterial conjunctivitis
B. Trachoma (Correct Answer)
C. Onchocerciasis
D. Viral conjunctivitis

Explanation: ***Trachoma*** - The **SAFE strategy** (Surgery, Antibiotics, Facial cleanliness, Environmental improvement) is the World Health Organization's primary intervention for eliminating blinding **trachoma**. - It addresses the various aspects of **trachoma transmission** and progression, from treating active infection to preventing reinfection and managing trichiasis. *Bacterial conjunctivitis* - This condition is typically treated with **topical antibiotics** and does not require a comprehensive, multi-component public health strategy like SAFE. - It is generally self-limiting and rarely leads to **blinding complications** or necessitates surgical intervention. *Onchocerciasis* - Also known as **river blindness**, this parasitic disease is primarily controlled through mass drug administration with **ivermectin**. - While it can cause severe visual impairment, its transmission cycle and treatment differ significantly from those addressed by the SAFE strategy. *Viral conjunctivitis* - This is usually a **self-limiting condition** for which there is no specific antiviral treatment, and management is primarily supportive. - It does not involve bacterial infection, chronic inflammation leading to fibrosis, or require the **public health interventions** outlined in the SAFE strategy.

Question 324: Which of the following is not a STD -

A. Amoebiasis
B. Herpes simplex type 1
C. Scabies
D. Hepatitis A (Correct Answer)

Explanation: ***Hepatitis A*** - **Hepatitis A** is primarily transmitted via the **fecal-oral route** through contaminated food or water, NOT through sexual contact. - While rare transmission can occur through oral-anal contact during sexual activity, it is **not classified as a sexually transmitted disease (STD)**. - Hepatitis A is a vaccine-preventable disease and is NOT included in standard STD classifications. *Amoebiasis* - **Amoebiasis**, caused by *Entamoeba histolytica*, is primarily a **gastrointestinal parasitic infection** transmitted through the **fecal-oral route** via contaminated food or water. - While it can occasionally be transmitted through oral-anal sexual contact (particularly in MSM populations), it is **not traditionally classified as an STD** in standard medical literature. - **NOTE**: This option is also debatable as "not an STD" and creates potential ambiguity in the question. *Herpes simplex type 1* - **Herpes simplex virus type 1 (HSV-1)** can cause both oral herpes (cold sores) and genital herpes through oral-genital sexual contact. - HSV-1 is increasingly recognized as a cause of **genital herpes** and is transmitted sexually, making it an **STD**. - While HSV-2 is the classic genital herpes virus, HSV-1 genital infections are becoming more common. *Scabies* - **Scabies** is a skin infestation caused by *Sarcoptes scabiei* mite, transmitted through **prolonged close physical contact**, including sexual contact. - It is **recognized as an STD** because sexual contact is a common mode of transmission in adults. - Scabies is highly contagious and easily spreads between sexual partners.

Question 325: Best emergency sanitary measure to control cholera is -

A. Chemoprophylaxis
B. Mass vaccination
C. Disinfection of stool
D. Provision of chlorinated water (Correct Answer)

Explanation: ***Provision of chlorinated water*** - Cholera is primarily a **waterborne disease**, and providing safe, chlorinated water is the most effective way to prevent its transmission in an emergency. - **Chlorination** kills *Vibrio cholerae* in water sources, significantly reducing the risk of infection. *Chemoprophylaxis* - While it can be used for close contacts or specific high-risk groups, **mass chemoprophylaxis** is not a sustainable or practical emergency measure for controlling widespread cholera outbreaks. - It carries risks of **antibiotic resistance** and doesn't address the underlying environmental source of contamination. *Mass vaccination* - **Oral cholera vaccines** are effective, but their deployment in an emergency is often challenged by logistics, time constraints, and the need for multiple doses, making it less immediate than securing safe water. - Vaccination provides **individual protection** but does not rapidly contain an ongoing outbreak if environmental sources of contamination persist. *Disinfection of stool* - **Disinfection of stool** from infected individuals is crucial for preventing local spread and protecting caregivers, but it does not address the broader community-level contamination of water sources. - This measure targets the **secondary transmission** route rather than the primary environmental reservoir.

Question 326: Target interventions of National AIDS Control Organisation include all, except?

A. Detection & treatment for sexually transmitted infections
B. Abscess prevention & management in injecting drug users
C. Condom promotion & distribution
D. Provision of lubricants to Injecting drug users (Correct Answer)

Explanation: ***Provision of lubricants to Injecting drug users*** - The provision of lubricants is primarily relevant for **safe sexual practices** to prevent friction and condom breakage, not directly for injecting drug users to mitigate injection-related risks. - While **harm reduction** is a key focus, this specific intervention does not align with the direct prevention of HIV transmission routes typically targeted for injecting drug users, such as shared needles or inadequate sterile practices. *Detection & treatment for sexually transmitted infections* - **STIs** increase the risk of HIV transmission by causing genital lesions and inflammation, thus their detection and treatment are crucial for HIV prevention. - This intervention is a cornerstone of National AIDS Control Organisation (NACO) programs to reduce HIV vulnerability in high-risk populations. *Abscess prevention & management in injecting drug users* - **Abscesses** are common complications of injecting drug use, often resulting from unsterile practices or shared needles, which are also routes for HIV transmission. - Addressing these complications is part of a broader **harm reduction strategy** aimed at minimizing health risks among injecting drug users, including HIV. *Condom promotion & distribution* - **Condom promotion and distribution** is a fundamental intervention for preventing sexual transmission of HIV by providing a physical barrier. - This is a central component of NACO's strategy to promote safer sexual practices among the general population and high-risk groups.

Question 327: Isolation period of Hepatitis A after the onset of jaundice is:

A. 4 weeks
B. 3 weeks
C. 2 weeks
D. 1 week (Correct Answer)

Explanation: ***1 week*** - Individuals with **Hepatitis A** are considered infectious for about **1 week** after the onset of **jaundice** or within 2 weeks of symptom onset. - This period is critical for implementing preventive measures like **handwashing** to prevent further spread. *4 weeks* - While viral shedding can occur for several weeks, the period of highest infectivity and public health concern typically extends for **1 week** post-jaundice. - Extending isolation to 4 weeks might be overly restrictive without a significant additional public health benefit in most cases. *3 weeks* - The peak period of **viral shedding** and infectivity for Hepatitis A generally occurs before and within the first week of jaundice. - By the third week post-jaundice, viral shedding has usually significantly decreased, making the individual much less infectious. *2 weeks* - Although some viral shedding can still occur, the most critical period for transmissibility has largely passed by the end of the **first week** after jaundice onset. - Most public health guidelines focus on measures during the period of highest risk to prevent widespread transmission.

Question 328: Screening age for trachoma is:

A. 9-14 years
B. Below 5 years school child only
C. 5-15 years
D. 1-9 years (Correct Answer)

Explanation: ***1-9 years*** - The **WHO recommends mass drug administration (MDA) for trachoma control** focused on communities where the prevalence of trachomatous inflammation—follicular (TF) in children aged **1–9 years** is 5% or more. - This age group is considered the **primary reservoir of infection** and crucial for transmission dynamics, making it the most appropriate target for screening and intervention. *9-14 years* - While older children can be infected, the **highest prevalence of active trachoma (TF and TI)** is typically found in younger children, making this age group less significant for initial screening compared to 1-9 years. - Screening this age group alone might miss a substantial portion of the **infectious reservoir**, limiting the effectiveness of control programs. *Below 5 years school child only* - This option is too restrictive as **trachoma also affects non-school-going children** and those slightly older than 5, but still within the 1-9 year primary target range. - **Excluding children in the 5-9 year group** would significantly reduce the impact of screening efforts, as younger school-age and pre-school children are highly susceptible. *5-15 years* - This age range is broader than the recommended primary screening age group and would include those for whom **active infection prevalence begins to decline**. - Focusing on a *broader and older* group might dilute resources that are most effectively used in the **1-9 year-old group**, where intervention has the greatest impact on transmission.

Question 329: Most important vector for Lyme disease transmission is -

A. Rat flea
B. Sand fly
C. Mosquito
D. Ticks (Correct Answer)

Explanation: ***Ticks*** - **Lyme disease** is caused by the bacterium *Borrelia burgdorferi* and is primarily transmitted to humans through the bite of infected black-legged ticks, also known as **deer ticks** (*Ixodes scapularis* in the eastern and midwestern U.S., and *Ixodes pacificus* in the Pacific Coast). - Ticks are the **definitive vector** for Lyme disease, serving as both a reservoir and a means of transmission. *Rat flea* - **Rat fleas** (*Xenopsylla cheopis*) are primarily known as vectors for diseases such as **bubonic plague** (caused by *Yersinia pestis*) and **murine typhus** (caused by *Rickettsia typhi*). - They are not associated with the transmission of Lyme disease. *Sand fly* - **Sand flies** (e.g., *Phlebotomus* species) are vectors for diseases such as **leishmaniasis**, **sandfly fever**, and **Bartonellosis**. - They are not responsible for transmitting *Borrelia burgdorferi* or Lyme disease. *Mosquito* - **Mosquitoes** are significant vectors for numerous diseases including **malaria**, **dengue fever**, **Zika virus**, and **West Nile virus**. - While they transmit many pathogens, mosquitoes do not transmit the bacteria responsible for Lyme disease.

Question 330: Most efficient larval control method to prevent transmission of urban malaria:

A. Filling of ditches and cesspools (Correct Answer)
B. Cleaning of drains
C. Covering overhead tanks
D. Uprooting of plants

Explanation: ***Filling of ditches and cesspools*** - This method eliminates **breeding sites** for mosquito larvae by removing stagnant water collections - Effective for **environmental source reduction**, a fundamental principle of larval control - Addresses both rural and urban malaria vector breeding sites including **Anopheles stephensi** in urban areas - Direct intervention at the **larval stage** prevents adult mosquito emergence *Cleaning of drains* - Important for sanitation and can reduce breeding sites for both **Anopheles stephensi** (urban malaria) and **Aedes** (dengue) in urban settings - However, drains are continuously replenished with water, making this less efficient as a long-term larval control measure - Requires frequent repetition to maintain effectiveness *Covering overhead tanks* - Highly effective for preventing **Anopheles stephensi** breeding in stored water, which is a significant source of urban malaria transmission - However, this is a **preventive measure** rather than an active larval control method - Does not eliminate existing larvae, only prevents new breeding *Uprooting of plants* - Reduces adult mosquito **resting sites** but does not directly address the **larval stage** - Not a larval control method and therefore not effective for preventing malaria transmission at the source

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