Infectious Diseases Practice Questions

Q: What is the duration that defines a permanent carrier for Hepatitis B Virus (HBV)?

More than 6 months. **Explanation:** The definition of a **chronic or permanent carrier** of Hepatitis B is based on the persistence of the **Hepatitis B surface Antigen (HBsAg)** in the blood for a specific duration. **1. Why Option A is Correct:** According to the World Health Organization (WHO) and standard epidemiological guidelines, a person is classified as a chronic carrier if HBsAg persists in the serum for **more than 6 months**. This duration is clinically significant because most acute HBV infections in adults resolve within 6 months. Persistence beyond this window indicates that the immune system has failed to clear the virus, leading to a chronic infection state. **2. Why Other Options are Incorrect:** * **Option B (1 month):** This represents the acute phase of infection. Many patients are HBsAg positive during the incubation and early symptomatic period but go on to clear the virus spontaneously. * **Options C & D (1 year / 2 years):** While a carrier will remain positive for these durations, the formal medical definition for "chronic" status is established much earlier (at the 6-month mark) to initiate monitoring for complications like cirrhosis or hepatocellular carcinoma. **3. High-Yield Clinical Pearls for NEET-PG:** * **Age Factor:** The risk of becoming a carrier is inversely proportional to age. Approximately **90% of infected newborns** become chronic carriers, compared to only **5–10% of infected adults**. * **Infectivity Marker:** While HBsAg defines the carrier state, **HBeAg** (Envelope Antigen) is the marker of high infectivity and active viral replication. * **Super-carrier:** A "super-carrier" is a person who is both HBsAg positive and HBeAg positive, possessing a very high viral load. * **Healthy Carrier:** Defined as HBsAg positive for >6 months but with normal ALT levels and low/undetectable HBV DNA.

Q: Which of the following is NOT an epidemiological feature of Japanese encephalitis?

Pigs can show clinical manifestations.. **Explanation:** Japanese Encephalitis (JE) is a zoonotic viral infection caused by a Group B Arbovirus (Flavivirus) and transmitted primarily by *Culex tritaeniorhynchus* mosquitoes. **Why Option C is the correct answer:** In the transmission cycle of JE, **pigs act as the "Amplifier Host."** While the virus multiplies rapidly in pigs, leading to high-titre viremia (which infects mosquitoes), the infection in pigs is **asymptomatic**. They do not show clinical manifestations of encephalitis. This makes them the perfect reservoir for maintaining the virus in the environment without dying off. **Analysis of other options:** * **Option A (Extra-human hosts):** JE is a zoonotic disease. The natural cycle involves extra-human hosts, primarily **Ardeid birds** (herons, egrets) as the natural reservoir and **pigs** as the amplifier host. * **Option B (Man is an incidental host):** Humans are "dead-end" hosts. Because the level of viremia in humans is low and transient, a mosquito biting an infected human cannot pick up enough virus to infect another person. * **Option D (Epidemics in Karnataka):** JE is endemic in several parts of India. Major outbreaks have been historically reported in states like Uttar Pradesh, Bihar, West Bengal, Assam, and South Indian states including **Karnataka** (especially the Bellary and Kolar districts) and Andhra Pradesh. **High-Yield NEET-PG Pearls:** * **Vector:** *Culex tritaeniorhynchus* (breeds in stagnant water/paddy fields). * **Reservoir/Maintenance Host:** Ardeid birds. * **Amplifier Host:** Pigs (Ratio of 1:1000—one infected pig can infect a thousand mosquitoes). * **Dead-end Hosts:** Humans and Horses. * **Vaccine:** Live attenuated **SA-14-14-2** (most common in India) or killed mouse brain-derived (Nakayama strain).

Q: What is the amount of trisodium citrate dihydrate in WHO ORS formulation?

2.9 gm. **Explanation:** The current **WHO Reduced Osmolarity ORS** is the standard treatment for dehydration due to diarrhea. The correct amount of **Trisodium citrate dihydrate** in one liter of this formulation is **2.9 grams**. **Why 2.9 gm is correct:** Trisodium citrate was introduced to replace Sodium bicarbonate (used in older formulations) because it increases the shelf-life of the ORS packets in tropical climates. Functionally, citrate acts as an alkalinizing agent that corrects metabolic acidosis resulting from diarrhea. Furthermore, it enhances the intestinal absorption of sodium and water. **Analysis of Incorrect Options:** * **1.5 gm (Option A):** This is the amount of **Potassium Chloride** in the WHO ORS formulation. * **2.6 gm (Option B):** This is the amount of **Sodium Chloride** (common salt) in the formulation. (Note: In the older "Standard" ORS, this was 3.5 gm). * **3.9 gm (Option D):** This value does not correspond to any constituent of the standard ORS formulation. **High-Yield Clinical Pearls for NEET-PG:** * **Total Osmolarity:** The reduced osmolarity ORS has a total osmolarity of **245 mOsm/L** (compared to 311 mOsm/L in the older version). This reduction helps decrease stool output and prevents hypernatremia. * **Glucose Concentration:** It contains **13.5 gm** of anhydrous glucose. The glucose-sodium co-transport mechanism remains intact even during viral or bacterial diarrhea. * **Composition Summary (per Liter):** * NaCl: 2.6 g * KCl: 1.5 g * Trisodium citrate: 2.9 g * Glucose: 13.5 g * **Electrolyte Concentrations:** Na+ (75 mmol/L), K+ (20 mmol/L), Cl- (65 mmol/L), Citrate (10 mmol/L), and Glucose (75 mmol/L).

Q: What is the web-based program for monitoring Tuberculosis (TB)?

Nikshay. **Explanation:** **Nikshay** is the correct answer. It is the unified web-based ICT (Information and Communication Technology) platform for TB surveillance in India, developed by the Ministry of Health and Family Welfare (MoHFW) in collaboration with NIC. It serves as the backbone of the **National Tuberculosis Elimination Program (NTEP)**, allowing for the notification of TB cases from both public and private sectors, tracking patient adherence, and facilitating the Direct Benefit Transfer (DBT) of incentives like the *Nikshay Poshan Yojana*. **Analysis of Incorrect Options:** * **Nischay:** This is a home-based pregnancy test kit provided under the National Health Mission (NHM) to ASHAs for early detection of pregnancy in the community. * **Nikusth:** This is the web-based reporting and monitoring system specifically designed for the **National Leprosy Eradication Programme (NLEP)**. * **e-DOTS:** While DOTS (Directly Observed Treatment, Short-course) is the strategy for TB treatment, "e-DOTS" is a generic term for electronic monitoring (like 99DOTS or MERM) rather than the name of the primary national web-based monitoring portal. **Clinical Pearls for NEET-PG:** * **Nikshay Poshan Yojana:** Provides ₹500/month to all TB patients for nutritional support throughout their treatment. * **Notification:** TB is a **notifiable disease** in India (since 2012); failure to notify by clinical establishments is a punishable offense under Section 269/270 of the IPC. * **Goal:** India aims to eliminate TB by **2025**, five years ahead of the global Sustainable Development Goal (SDG) of 2030.

Q: How frequently should a health worker visit all houses in their area to check for malaria cases?

Fortnightly. **Explanation:** The correct answer is **Fortnightly (Option B)**. This frequency is a cornerstone of the **Active Case Detection (ACD)** strategy under the National Vector Borne Disease Control Programme (NVBDCP) for Malaria. **Why Fortnightly?** The primary objective of ACD is to identify fever cases, collect blood smears (thick and thin), and provide presumptive treatment. The fortnightly (once every 14 days) interval is strategically chosen based on the **incubation period of Malaria** (typically 10–14 days for *P. falciparum* and *P. vivax*). By visiting every 14 days, the health worker ensures that any new infection that has progressed to the symptomatic stage is detected and treated before the patient can become a source of further transmission to mosquitoes. **Analysis of Incorrect Options:** * **Weekly (A):** While more frequent, it is logistically demanding and unnecessary given the parasite's incubation period. * **Monthly (C):** Too infrequent. A patient could remain symptomatic and infectious for weeks, leading to local outbreaks and increased morbidity. * **Yearly (D):** This is irrelevant for acute infectious disease surveillance and is typically used for chronic disease prevalence surveys. **High-Yield Clinical Pearls for NEET-PG:** * **ACD vs. PCD:** Active Case Detection is done by health workers via house-to-house visits (Fortnightly). Passive Case Detection (PCD) occurs when a patient voluntarily visits a health facility. * **Annual Parasite Incidence (API):** The most sensitive indicator for measuring the malaria burden in a community. * **Drug of Choice:** For *P. vivax*, it is Chloroquine (3 days) + Primaquine (14 days). For *P. falciparum*, it is ACT (Artesunate Combination Therapy) + single dose Primaquine on Day 2. * **Surveillance Indicator:** The **Annual Blood Examination Rate (ABER)** should ideally be **>10%** to ensure effective surveillance.

Q: Which of the following are vectors for zoonotic disease transmission?

Ticks, rat fleas, sand flies, mosquitoes, and mites. **Explanation:** Zoonotic diseases are infections naturally transmitted between vertebrate animals and humans. Many of these diseases require **arthropod vectors** to bridge the gap between animal reservoirs and human hosts. **Why Option D is Correct:** Option D is the most comprehensive list. Each of these arthropods plays a critical role in transmitting major zoonotic pathogens: * **Ticks:** Transmit Kyasanur Forest Disease (KFD), Lyme disease, and Crimean-Congo hemorrhagic fever. * **Rat Fleas (*Xenopsylla cheopis*):** The classic vector for Bubonic Plague (*Yersinia pestis*) and Endemic typhus. * **Sand flies:** Transmit Leishmaniasis (Kala-azar), which has significant animal reservoirs (canines/rodents). * **Mosquitoes:** Transmit Japanese Encephalitis (pigs/herons as reservoirs) and Yellow Fever (monkeys). * **Mites:** Specifically, the Trombiculid mite transmits Scrub Typhus (*Orientia tsutsugamushi*), a major cause of acute febrile illness in India. **Why Other Options are Incorrect:** Options A, B, and C are **incomplete**. While the vectors listed in those options do transmit zoonotic diseases, they omit at least one essential vector included in the comprehensive list (Option D). In NEET-PG, when multiple options are factually "true," the most inclusive and complete option is the correct choice. **High-Yield Clinical Pearls for NEET-PG:** * **Scrub Typhus (Mites):** Look for the characteristic "Eschar" (painless ulcer with a black crust) in clinical vignettes. * **KFD (Ticks):** Also known as "Monkey Fever"; endemic to the Western Ghats of India. * **Plague (Rat Fleas):** Remember the "Blocked Flea" phenomenon caused by *Yersinia pestis* multiplication in the flea's proventriculus. * **Japanese Encephalitis:** Pigs are considered "amplifier hosts," while mosquitoes (*Culex tritaeniorhynchus*) are the vectors.

Question 1

What is the duration that defines a permanent carrier for Hepatitis B Virus (HBV)?

Accepted Answer

More than 6 months

Answer

More than 1 month

Answer

More than 1 year

Answer

More than 2 years

Question 2

Which of the following is NOT an epidemiological feature of Japanese encephalitis?

Accepted Answer

Pigs can show clinical manifestations.

Answer

The virus infects extra-human hosts.

Answer

Man is an incidental host.

Answer

Epidemics have been reported in Karnataka.

Question 3

What is the amount of trisodium citrate dihydrate in WHO ORS formulation?

Accepted Answer

2.9 gm

Answer

1.5 gm

Answer

2.5 gm

Answer

3.9 gm

Question 4

In the National Malaria Eradication Programme (NMEP), what is recommended for an area with API (Annual Parasite Incidence) of 2, except for?

Accepted Answer

Follow-up of every case for one year and monthly blood smears

Answer

Presumptive treatment

Answer

DDT spraying regularly throughout the year

Answer

Epidemiological investigation of all cases

Question 5

What is the web-based program for monitoring Tuberculosis (TB)?

Accepted Answer

Nikshay

Answer

Nischay

Answer

Nikusth

Answer

e-DOTS

Question 6

How frequently should a health worker visit all houses in their area to check for malaria cases?

Accepted Answer

Fortnightly

Answer

Weekly

Answer

Monthly

Answer

Yearly

Question 7

What is the recommended dose of Rabies immunoglobulin?

Accepted Answer

20 IU/kg body weight

Answer

10 IU/Kg body weight

Answer

15 IU/kg body weight

Answer

25 IU/kg body weight

Question 8

Which of the following statements regarding Japanese Encephalitis is true?

Accepted Answer

An epidemic is declared if there are 2-3 cases in a village.

Answer

70% of cases are reported from infants.

Answer

The ratio of clinical apparent to non-apparent infections is 1:100.

Answer

Mosquito bite is always associated with the disease.

Question 9

Prevention of human brucellosis depends primarily on?

Accepted Answer

Pasteurization of dairy products derived from goats, sheep, or cows

Answer

Treatment of human cases

Answer

Control of the insect vector

Answer

Immunization of farmers and slaughterhouse workers

Question 10

Which of the following are vectors for zoonotic disease transmission?

Accepted Answer

Ticks, rat fleas, sand flies, mosquitoes, and mites

Answer

Ticks, rat fleas, sand flies, and mosquitoes

Answer

Ticks, sand flies, mosquitoes, and mites

Answer

Rat fleas, sand flies, mosquitoes, and mites

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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