Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 631: Among the following options, the minimum acceptable Rideal-Walker coefficient for disinfectant used for cholera stool would be?

A. 4
B. 10
C. 2 (Correct Answer)
D. 7

Explanation: ***2 (Minimum acceptable among given options)*** - The **Rideal-Walker coefficient** measures disinfectant efficacy relative to phenol as the standard reference - A coefficient of **2** means the disinfectant is **twice as effective** as phenol against test organisms (*Salmonella typhi* and *Staphylococcus aureus*) - While higher coefficients are preferred for highly infectious materials like cholera stool, **2 represents the minimum acceptable threshold** among the given options that still provides reasonable disinfection efficacy - Standard practice recommends disinfectants with RW coefficient ≥5 for cholera stool, but among the choices provided, 2 is the lowest that meets basic acceptability criteria *4 (Better choice but not the minimum)* - A coefficient of **4** means the disinfectant is **four times more effective** than phenol - This provides **more robust disinfection** and would be preferred over a coefficient of 2 - However, the question specifically asks for the **minimum acceptable** value, not the optimal value - Among the options, this is not the minimum *7 (Highly effective)* - A coefficient of **7** indicates the disinfectant is **seven times more potent** than phenol - This represents **very good disinfection efficacy** and exceeds minimum requirements - This is well above the minimum acceptable threshold *10 (Excellent efficacy)* - A coefficient of **10** means the disinfectant is **ten times more effective** than phenol - This represents **excellent disinfection power** with a very high safety margin - While ideal for high-risk situations, this far exceeds the minimum acceptable requirement

Question 632: 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 633: Human, animal, fomite or objects from which infective organism enters the host is called?

A. Infective Reservoir
B. Infective Carrier
C. None of the above
D. Source of infection (Correct Answer)

Explanation: ***Source of infection*** - The **source of infection** refers to the person, animal, object, or substance from which an infectious agent passes immediately to a host. - This can include humans, animals, fomites, or contaminated objects that directly transmit the infectious organism. - This is the proximate source from which the agent enters the host. *Infective Reservoir* - An **infective reservoir** is the long-term habitat where an infectious agent normally lives, grows, and multiplies. - The reservoir can be human, animal, plant, soil, or inanimate matter where the agent is normally found. - While a reservoir can be a source, the source is specifically the immediate point from which transmission occurs. *Infective Carrier* - An **infective carrier** is an infected person or animal that harbors a specific infectious agent without showing clinical symptoms but can transmit it to others. - A carrier is a type of source (when transmission occurs from them), but the term "source" is broader, encompassing inanimate objects and fomites as well. *None of the above* - This option is incorrect because **Source of infection** accurately describes the concept presented in the question.

Question 634: What is a major sign for AIDS surveillance in the WHO case definition?

A. Weight loss greater than 10% (Correct Answer)
B. Chronic cough for more than 1 month
C. Generalized lymphadenopathy
D. Disseminated herpes infection

Explanation: ***Weight loss greater than 10%*** - **Weight loss >10% of body weight** is one of the **three major signs** in the WHO clinical case definition for AIDS surveillance. - The **three major signs** are: (1) Weight loss >10%, (2) Chronic diarrhea >1 month, and (3) Prolonged fever >1 month. - This symptom reflects **"wasting syndrome,"** a severe manifestation of advanced HIV disease indicating significant metabolic and immunological dysfunction. - Major signs are critical for AIDS surveillance, especially in resource-limited settings where laboratory diagnosis may not be readily available. *Chronic cough for more than 1 month* - This is classified as a **minor sign**, not a major sign, in the WHO AIDS surveillance definition. - While chronic cough can indicate opportunistic infections like tuberculosis or *Pneumocystis jirovecii* pneumonia in HIV-infected individuals, it does not meet the criteria for a major sign. - WHO clinical staging requires major signs to have greater specificity for advanced disease. *Generalized lymphadenopathy* - **Generalized lymphadenopathy** is a **minor sign** in the WHO case definition. - Also known as Persistent Generalized Lymphadenopathy (PGL), it is common in early to chronic HIV infection but does not typically signify AIDS-stage disease. - It involves lymph node enlargement in two or more non-contiguous sites (excluding inguinal nodes) for more than 3 months. *Disseminated herpes infection* - Chronic progressive or disseminated herpes simplex infection is classified as a **minor sign**, not a major sign. - While severe herpes infections (including recurrent herpes zoster) are associated with immunosuppression in HIV, they are part of the minor criteria in WHO AIDS surveillance. - Major signs are reserved for more specific indicators of severe immunodeficiency and wasting.

Question 635: Most effective preventive measure against rabies

A. Heat
B. Humidity
C. Avoiding contact with infected animals and vaccination (Correct Answer)
D. None of the options

Explanation: ***Avoiding contact with infected animals and vaccination*** ✓ - The most effective preventive measure against rabies is to **avoid contact with potentially infected animals**, especially wild animals and unvaccinated domestic animals. - **Vaccination** (pre-exposure prophylaxis) is crucial for individuals at high risk of exposure (veterinarians, animal handlers, laboratory workers) and for domestic animals, forming the cornerstone of rabies prevention. - Post-exposure prophylaxis (PEP) with immunoglobulin and vaccine series is highly effective when administered promptly after exposure. *Heat* - While high temperatures can inactivate the rabies virus in a laboratory setting, it is **not a practical or effective preventive measure** against rabies in real-world scenarios. - The virus is transmitted through bites, scratches, and mucous membrane contact with infected saliva; environmental heat does not prevent transmission or infection. *Humidity* - **Humidity does not play a significant role** in the prevention or transmission of rabies. - The rabies virus is labile outside of a host and does not survive long in the environment, regardless of humidity levels. *None of the options* - This option is incorrect because there are highly effective preventive measures against rabies, as detailed in the correct option. - Rabies prevention is well-established through public health interventions (animal vaccination programs, post-exposure prophylaxis) and individual precautions.

Question 636: Which of the following diseases is NOT transmitted by sandflies?

A. Visceral Leishmaniasis
B. Oriental sore
C. Relapsing fever (Correct Answer)
D. Cutaneous Leishmaniasis

Explanation: ***Relapsing fever*** - **Relapsing fever** is primarily transmitted by **ticks** (tick-borne relapsing fever) or **lice** (louse-borne relapsing fever), not sandflies. - It is caused by **spirochetes** of the genus *Borrelia*, which are distinct from the *Leishmania* parasites transmitted by sandflies. *Cutaneous Leishmaniasis* - **Cutaneous leishmaniasis** is a **sandfly-borne disease** caused by *Leishmania* parasites, leading to skin sores. - Sandflies (genus **Phlebotomus** in the Old World and **Lutzomyia** in the New World) transmit these parasites. *Visceral Leishmaniasis* - **Visceral leishmaniasis**, also known as **kala-azar**, is a severe form of leishmaniasis transmitted by the bite of **infected female sandflies**. - It affects internal organs like the **spleen**, **liver**, and **bone marrow**. *Oriental sore* - **Oriental sore** is another name for **cutaneous leishmaniasis**, indicating that it is also transmitted by **sandflies**. - It refers to the characteristic **skin lesions** caused by *Leishmania* parasites following a sandfly bite.

Question 637: All of the following are anthropozoonosis except

A. Rabies
B. Plague
C. Anthrax
D. Schistosomiasis (Correct Answer)

Explanation: ***Schistosomiasis*** - This is a **human-to-human** disease, even though it involves an intermediate **snail host**. - Its life cycle does not involve transmission of pathogens from vertebrate animals to humans. *Rabies* - Rabies is a classic **anthropozoonosis**, transmitted to humans primarily through the saliva of infected animals, most commonly **dogs** and **bats**. - It involves a pathogen (rabies virus) that cycles between animals and can be transmitted to humans. *Plague* - Plague is an **anthropozoonosis** caused by *Yersinia pestis*, typically transmitted from **rodents** (e.g., rats) to humans via flea bites. - The disease maintains a natural reservoir in wild rodent populations, making it a prime example of animal-to-human transmission. *Anthrax* - Anthrax is an **anthropozoonosis** caused by *Bacillus anthracis*, transmitted to humans from infected **livestock** (e.g., cattle, sheep). - Humans usually acquire the infection through contact with infected animals or their products, or by inhaling spores.

Question 638: In which condition is a night blood survey performed?

A. Lymphatic filariasis (Correct Answer)
B. Typhoid fever
C. Malaria infection
D. Visceral leishmaniasis

Explanation: ***Lymphatic filariasis*** - A **night blood survey** is crucial for diagnosing lymphatic filariasis because the microfilariae of species like *Wuchereria bancrofti* and *Brugia malayi* exhibit **nocturnal periodicity**, meaning they are most abundant in peripheral blood between 10 PM and 2 AM. - Collecting blood at night maximizes the chance of detecting these parasites, which are responsible for the disease. *Typhoid fever* - Diagnosis of **typhoid fever** primarily relies on **blood cultures** taken during the febrile phase, or stool/urine cultures later in the disease. - A night blood survey is not relevant for detecting the causative bacterium, *Salmonella Typhi*. *Malaria infection* - While a **blood smear** is essential for diagnosing malaria, the timing of blood collection is less critical than for filariasis, although peak parasite density can vary. - **Malaria parasites** are typically detected in blood samples taken during symptomatic periods, regardless of specific time of day. *Visceral leishmaniasis* - **Visceral leishmaniasis** is diagnosed by detecting parasites in samples from **bone marrow**, spleen, or lymph nodes, or through serological tests for antibodies. - A night blood survey is not used in the diagnosis of *Leishmania donovani* infection.

Question 639: Which of the following IS included in the NVBDCP?

A. Leprosy
B. Malaria
C. Dengue
D. Chikungunya (Correct Answer)

Explanation: ***Chikungunya*** - **Chikungunya** is one of the six diseases covered under the **National Vector Borne Disease Control Programme (NVBDCP)** in India. - The NVBDCP specifically includes: **Malaria, Dengue, Chikungunya, Lymphatic Filariasis, Kala-azar (Visceral Leishmaniasis), and Japanese Encephalitis**. - Chikungunya, transmitted by *Aedes* mosquitoes, represents a significant public health concern requiring vector control measures. *Leprosy* - **Leprosy** is NOT covered under NVBDCP as it is **not a vector-borne disease**. - Leprosy is caused by *Mycobacterium leprae* and spreads through prolonged close contact with infected individuals, not through vectors. - It is managed under a separate program: **National Leprosy Eradication Programme (NLEP)**. *Malaria* - **Malaria** is indeed included in NVBDCP and is actually the **primary focus** of the program. - However, since the question asks for which disease IS included and all vector-borne options would be correct, the presence of Leprosy as a distractor makes Chikungunya the correct choice among valid NVBDCP diseases. *Dengue* - **Dengue** is also covered under NVBDCP as one of the six priority vector-borne diseases. - Like Malaria and Chikungunya, Dengue receives focused surveillance and control interventions under this national program.

Question 640: Which of the following statements best describes the operational definition of onchocerciasis elimination?

A. All interventions have been successfully implemented.
B. There is no recrudescence of the disease after a defined period.
C. All of the options are true.
D. Transmission of O. volvulus has been reduced to a level where it cannot sustain itself in the population. (Correct Answer)

Explanation: **Transmission of O. volvulus has been reduced to a level where it cannot sustain itself in the population.** - This statement accurately reflects the definition of **disease elimination**, where the incidence of infection is reduced to zero in a defined geographical area, signifying that the **transmission cycle can no longer be sustained**. - For onchocerciasis, this means the **vector (blackfly)** is no longer transmitting the parasite (*Onchocerca volvulus*) between humans at a rate that allows the disease to persist. *All interventions have been successfully implemented.* - While successful implementation of interventions is crucial for elimination, it is a **process goal**, not the **ultimate outcome** or operational definition of elimination itself. - Elimination is defined by the **absence of sustained transmission**, which is a direct measure of disease burden, not intervention fidelity. *There is no recrudescence of the disease after a defined period.* - The **absence of recrudescence** (re-emergence) after a defined period is an important indicator of successful elimination validation, but it is a **consequence** or **part of the verification process**, not the primary operational definition. - The operational definition focuses on the **state of transmission** that leads to this sustained absence. *All of the options are true.* - This option is incorrect because only one of the provided statements accurately describes the **operational definition of elimination** in the context of parasitic diseases like onchocerciasis. - The other options describe aspects related to the elimination process or its verification, but not the core definition.

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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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