Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 461: Every TB sputum positive patient can infect up to

A. 1-2 persons per year
B. 10-15 persons per year (Correct Answer)
C. 5-6 persons per year
D. 100-200 persons per year

Explanation: ***10-15 persons per year*** - Each **sputum smear-positive** tuberculosis patient can infect a substantial number of close contacts annually due to the highly contagious nature of **Mycobacterium tuberculosis** via airborne transmission. - This high infectivity rate underscores the importance of prompt diagnosis and treatment to limit disease spread in the community. *1-2 persons per year* - This number is significantly **too low** for a sputum-positive TB patient, who is actively shedding viable bacilli and poses a much higher risk of transmission. - Such a low rate might be associated with less contagious forms of TB, but not sputum-positive pulmonary TB. *5-6 persons per year* - While higher than 1-2, this number still **underestimates the typical infectivity** of an active, sputum-positive TB case. - The potential for infection is greater, especially in conditions of close contact and poor ventilation. *100-200 persons per year* - This figure represents an **overestimation** of the average number of people infected by a single TB patient. - While TB can spread rapidly in specific high-risk settings, such a high general transmission rate is not commonly observed.

Question 462: Which of the following is/are objectives of the Roll Back Malaria program?

A. Encourage the development of more effective and new anti malarial drugs and vaccines
B. Encourage the proper and expanded use of insecticide treated mosquito nets
C. All of the above (Correct Answer)
D. Training of village health workers and mothers on early and appropriate treatment of malaria

Explanation: ***All of the above*** - The **Roll Back Malaria Partnership (RBM)** is a comprehensive global initiative launched in 1998 to coordinate international action against malaria. - The program adopts a **multi-faceted approach** that includes all three strategies: promoting development of **new treatments and vaccines**, expanding the use of **insecticide-treated mosquito nets (ITNs)**, and empowering **community health workers** for early diagnosis and treatment. - All the listed options represent core pillars of the RBM strategy, making this the correct answer. *Encourage the development of more effective and new anti malarial drugs and vaccines* - This is indeed one component of the RBM program's strategy, focusing on **research and development**. - However, this alone does not encompass the entire program's scope. *Encourage the proper and expanded use of insecticide treated mosquito nets* - This is a critical **vector control intervention** promoted by RBM to reduce mosquito bites and prevent transmission. - While essential, it represents only one pillar of the comprehensive program. *Training of village health workers and mothers on early and appropriate treatment of malaria* - This aspect emphasizes **community engagement** and capacity building for timely diagnosis and case management. - It falls under improving **access to treatment** and strengthening healthcare systems, but is not the entirety of the program.

Question 463: Which diseases are infectious but not communicable?

A. Tetanus (Correct Answer)
B. Mumps
C. Scarlet fever
D. Measles

Explanation: **Key Concept:** Infectious diseases are caused by microorganisms, while communicable diseases can spread from person to person. Some diseases are infectious but NOT communicable. ***Correct: Tetanus*** - Tetanus is caused by toxins produced by *Clostridium tetani*, which typically enters the body through **wounds contaminated with soil or feces** - It is **infectious** because a microorganism causes the disease - It is **NOT communicable** as it **cannot be spread directly from person to person** - the bacteria must enter through environmental contamination - Classic example of infectious but non-communicable disease *Incorrect: Mumps* - Mumps is a **communicable disease** caused by the mumps virus, primarily spread through **respiratory droplets** from person to person - Leads to inflammation of **salivary glands**, especially the parotid glands - Both infectious AND communicable *Incorrect: Scarlet fever* - Scarlet fever is a **communicable bacterial infection** caused by group A *Streptococcus*, spread through **respiratory droplets** from person to person - Presents with a characteristic **red rash**, sore throat, and fever - Both infectious AND communicable *Incorrect: Measles* - Measles is a **highly communicable viral disease** transmitted through **airborne droplets** from person to person - Characterized by a distinctive **rash, fever, cough, coryza, and conjunctivitis** - Both infectious AND communicable

Question 464: Which of the following diseases is cyclopropagative?

A. Malaria (Correct Answer)
B. Filaria
C. Plague
D. None of the options

Explanation: ***Malaria*** - **Malaria** is a **cyclopropagative** disease because the causative agent, *Plasmodium* parasites, undergoes both **cyclical development** and **multiplication** within the mosquito vector. - The parasite's life cycle in the **Anopheles mosquito** involves sexual reproduction (sporogony) and asexual reproduction, leading to an increased number of infective stages (sporozoites). *Filaria* - **Filaria** is a **cyclodevelopmental** disease, meaning the parasitic worms (nematodes) develop cyclically within the vector (e.g., mosquito, blackfly) but **do not multiply** in number. - The vector transmits the microfilariae, which then mature within the human host, but the number of parasites in the vector remains stable, making it non-propagative. *Plague* - **Plague** is caused by the bacterium *Yersinia pestis* and is transmitted by fleas, but it is not a cyclopropagative disease. - While the bacteria multiply within the flea, this transmission is primarily **mechanical** or via a blocked flea foregut, rather than undergoing a complex developmental cycle with propagation like *Plasmodium*. *None of the options* - This option is incorrect because **malaria** clearly fits the definition of a **cyclopropagative disease** due to the multiplication and cyclical development of *Plasmodium* in its vector.

Question 465: Which of the following vectors is responsible for the highest burden of vector-borne diseases globally?

A. Sand flea
B. House fly
C. Mosquito (Correct Answer)
D. Mite

Explanation: ***Correct: Mosquito*** - **Mosquitoes** are responsible for transmitting a wide array of devastating diseases, including **malaria**, **dengue**, **Zika virus**, **chikungunya**, **yellow fever**, **Japanese encephalitis**, and **lymphatic filariasis**, leading to hundreds of millions of infections and hundreds of thousands of deaths annually. - Their global distribution, high reproductive rate, and ability to adapt to diverse environments contribute to their significant impact on public health worldwide. - Malaria alone causes over 200 million cases and approximately 600,000 deaths per year, making mosquitoes the deadliest vector globally. *Incorrect: Sand flea* - **Sand fleas** (Tunga penetrans) are responsible for **tungiasis**, a parasitic skin condition, primarily in disadvantaged communities in tropical and subtropical regions. - While it causes significant morbidity and disability, it does not exert the same global burden in terms of mortality and widespread disease outbreaks as mosquito-borne illnesses. *Incorrect: House fly* - **House flies** (Musca domestica) can mechanically transmit various pathogens, including bacteria (e.g., Shigella, Salmonella) and viruses, contributing to gastrointestinal infections. - However, they act primarily as **mechanical vectors** and are not responsible for the direct transmission of dedicated vector-borne diseases with the same catastrophic global impact as mosquitoes. *Incorrect: Mite* - **Mites** are vectors for diseases such as **scrub typhus** (chigger mites) and can cause or transmit conditions like **scabies**. - While these diseases pose localized public health challenges, their global disease burden is considerably lower compared to mosquito-borne diseases.

Question 466: What is the incubation period of Hepatitis A?

A. 6 days – 6 weeks
B. 6 weeks – 6 months
C. 2 weeks – 2 months (Correct Answer)
D. 2 days – 2 weeks

Explanation: ***2 weeks – 2 months*** - The incubation period for **Hepatitis A** specifically ranges from **15 to 50 days (average 28 days)**, which falls within the 2 weeks to 2 months timeframe. - This period allows for viral replication before the onset of clinical symptoms like **jaundice**, **fatigue**, and **nausea**. *6 days – 6 weeks* - This range is too broad and includes periods that are either too short or too long for the typical **Hepatitis A** incubation, although 6 weeks is close to the upper limit. - While 6 weeks does fall within the possible maximum, the lower end of 6 days is uncharacteristically short for **Hepatitis A**. *6 weeks – 6 months* - This incubation period is generally too long for **Hepatitis A**, which rarely exceeds 50 days. - Longer incubation periods, such as **6 weeks to 6 months**, are more characteristic of other viral hepatitides like **Hepatitis B** or **Hepatitis C**. *2 days – 2 weeks* - This period is generally too short for the incubation of **Hepatitis A virus**. - Such a short incubation period is more typical for **bacterial food poisoning** or other acute gastrointestinal infections rather than viral hepatitis.

Question 467: False about Japanese encephalitis:

A. Case fatality rate is about 20-40%
B. Man to Man transmission (Correct Answer)
C. Pigs are amplifier hosts
D. Culicine mosquitoes are vectors

Explanation: ***Man to Man transmission*** - Japanese encephalitis is a **zoonotic disease** primarily transmitted between animals (especially pigs and birds) and mosquitoes. - Humans are considered **dead-end hosts**, meaning they do not develop a high enough viral load in their blood to infect mosquitoes, thus preventing direct human-to-human transmission. *Case fatality rate is about 20-40%* - The **case fatality rate** for Japanese encephalitis is indeed high, typically ranging from 20% to 30%, but can be up to 40% in some outbreaks. - This makes the statement **true**, as it accurately reflects the severe prognosis of the disease. *Pigs are amplifier hosts* - **Pigs** play a crucial role as **amplifier hosts** in the Japanese encephalitis transmission cycle. - They become highly viremic and thus significantly increase the amount of virus circulating in the environment, which can then be picked up by mosquitoes. *Culicine mosquitoes are vectors* - **Culicine mosquitoes**, particularly *Culex tritaeniorhynchus*, are the primary vectors responsible for transmitting the Japanese encephalitis virus. - These mosquitoes typically breed in **rice paddies** and other agricultural areas.

Question 468: Mammalian reservoir of Rickettsial pox -

A. Cattle
B. Goat
C. Mice (Correct Answer)
D. Human

Explanation: ***Mice*** - The primary **mammalian reservoir** for *Rickettsia akari*, which causes **rickettsialpox**, is **mice** (specifically the house mouse, *Mus musculus*). - The disease is transmitted to humans by the bite of the **mouse mite** (*Liponyssoides sanguineus*), which is the vector. *Cattle* - **Cattle** are not known reservoirs for *Rickettsia akari* or agents causing **rickettsialpox**. - They are more commonly associated with other zoonotic diseases such as **anthrax** or **Q fever** (*Coxiella burnetii*). *Goat* - **Goats** are not considered reservoirs for *Rickettsia akari* or the transmission of **rickettsialpox**. - They can be reservoirs for diseases like **brucellosis** or **Q fever**, but not for rickettsialpox. *Human* - **Humans** are occasional and **dead-end hosts** for *Rickettsia akari*, meaning they can get the disease but do not typically transmit it further to maintain the natural cycle. - Humans become infected when bitten by an infected **mouse mite** but do not act as the reservoir.

Question 469: KFD is transmitted by:

A. Sandfly
B. Mosquito
C. Tick (Correct Answer)
D. Mite

Explanation: ***Tick*** - KFD, or **Kyasanur Forest Disease**, is a viral hemorrhagic fever endemic to India that is primarily transmitted by infected **ticks**, specifically *Haemaphysalis spinigera*. - Humans can contract the disease through a **tick bite** or contact with an **infected animal**, such as monkeys, which are reservoirs for the virus. *Sandfly* - **Sandflies** are vectors for diseases such as **leishmaniasis** and **bartonellosis**, not Kyasanur Forest Disease. - These insects transmit parasites or bacteria, whereas KFD is a **viral infection** transmitted by ticks. *Mosquito* - **Mosquitoes** are common vectors for many viral diseases, including **dengue**, **malaria**, and **chikungunya**, but they do not transmit Kyasanur Forest Disease. - KFD is exclusively associated with **tick transmission** in its endemic regions. *Mite* - **Mites** can transmit diseases like **scrub typhus** (via chiggers) or cause conditions like **scabies**, but they are not vectors for Kyasanur Forest Disease. - The primary vector for KFD is the **hard tick**.

Question 470: NVBDCP includes all except ?

A. Filariasis
B. Malaria
C. Kala-azar
D. Yellow fever (Correct Answer)

Explanation: ***Yellow fever*** - Yellow fever is a **viral hemorrhagic fever** transmitted by infected mosquitoes, primarily **Aedes aegypti**. - While a significant public health concern, it is **not included in India's National Vector-Borne Disease Control Programme (NVBDCP)**, as it is not endemic to India. *Filariasis* - **Lymphatic filariasis** (elephantiasis) is a major vector-borne disease in India, caused by parasitic worms transmitted by mosquitoes. - It is a key component of the NVBDCP, which focuses on its elimination through **mass drug administration** and vector control. *Malaria* - **Malaria**, caused by Plasmodium parasites transmitted by Anopheles mosquitoes, is a cornerstone of the NVBDCP. - The program actively implements strategies for **case detection, treatment, vector control**, and preventing outbreaks. *Kala-azar* - **Kala-azar** (visceral leishmaniasis) is a severe parasitic disease transmitted by **sandflies**, making it a vector-borne disease. - It is one of the six diseases targeted by the NVBDCP for elimination, particularly in endemic regions of India.

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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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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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