Infectious Diseases Practice Questions

Q: What caused the maximum damage to Napoleon's army during his march to Moscow?

Typhus. **Explanation:** The correct answer is **Typhus** (specifically Epidemic Typhus). Napoleon’s 1812 Russian campaign is a classic historical example of how infectious diseases can alter the course of history. **1. Why Typhus is Correct:** Epidemic Typhus is caused by **_Rickettsia prowazekii_** and is transmitted by the **human body louse** (*Pediculus humanus corporis*). During the march to Moscow, the Grande Armée faced severe overcrowding, lack of hygiene, and cold weather—conditions that favored louse infestation. It is estimated that Napoleon lost more soldiers to Typhus (over 100,000) than to actual combat with the Russian army. **2. Why the other options are incorrect:** * **Plague:** Caused by *Yersinia pestis*, it was a major historical killer (e.g., Black Death), but it was not the primary driver of mortality in the 1812 campaign. * **Diarrhea/Dysentery:** While present due to poor sanitation, these were secondary to the massive Typhus outbreaks. * **Typhoid:** Caused by *Salmonella typhi*, it is water-borne. While it plagued many 19th-century armies, the specific "Great Killer" of the Russian campaign was the louse-borne Typhus. **NEET-PG High-Yield Pearls:** * **Vector:** Body louse (Typhus) vs. Rat flea (Plague) vs. Tick (Rocky Mountain Spotted Fever). * **Weil-Felix Test:** A classic (though non-specific) diagnostic test for Rickettsial infections. Epidemic Typhus shows a positive reaction with **OX-19**. * **Brill-Zinsser Disease:** A recrudescent (latent) form of Epidemic Typhus occurring years after the primary attack. * **Drug of Choice:** Doxycycline is the gold standard for all Rickettsial diseases.

Q: What is the quarantine period for yellow fever?

6 days. **Explanation:** The correct answer is **6 days**. In public health and international health regulations, the quarantine period for a disease is traditionally defined as the **maximum incubation period** of that specific infection. For Yellow Fever, the incubation period typically ranges from 3 to 6 days. Therefore, to ensure that an individual arriving from an endemic zone is not carrying the virus, they must be quarantined for the maximum duration of 6 days from the date of last possible exposure. **Analysis of Options:** * **A & B (1-2 days):** These are incorrect as they are shorter than the minimum incubation period; symptoms would likely not have manifested yet. * **C (6 days):** This is the **correct** answer, representing the maximum incubation period as per WHO International Health Regulations (IHR). * **D (10 days):** While the Yellow Fever vaccine becomes legally valid and provides immunity **10 days** after administration, this is not the quarantine period. **High-Yield Clinical Pearls for NEET-PG:** * **Vaccine Validity:** The Yellow Fever vaccine (17D strain) is valid for **life** (as per WHO 2016 update), but for international travel certificates, it becomes valid **10 days after vaccination**. * **Vector:** Primarily *Aedes aegypti* (Urban cycle) and *Haemagogus* (Jungle cycle). * **India Status:** India is "Yellow Fever receptive" (has the vector but not the virus). Hence, strict quarantine rules apply to travelers from the African and South American endemic belts. * **Contraindication:** The vaccine is a live attenuated vaccine and is contraindicated in infants <6 months, pregnant women, and immunocompromised individuals.

Q: What is true about poliomyelitis?

Increased muscular activity leads to increased paralysis.. **Explanation:** **Why Option C is Correct:** In poliomyelitis, the severity of paralysis is influenced by physical activity during the **pre-paralytic stage**. Increased muscular activity or trauma (like intramuscular injections) leads to increased vascularity in the corresponding segment of the spinal cord. This allows more viruses to reach the anterior horn cells, resulting in more extensive neuronal damage and severe paralysis. This phenomenon is known as **"Provocation Paralysis."** **Analysis of Incorrect Options:** * **Option A:** Inapparent (asymptomatic) infection is the most common form, occurring in over 91-95% of cases. Paralytic polio is the rarest form, occurring in less than 1% of infections. * **Option B:** Poliovirus specifically destroys the **Anterior Horn Cells** of the spinal cord (Lower Motor Neuron). Therefore, it causes **Flaccid Paralysis**, characterized by loss of muscle tone and absent deep tendon reflexes, not spastic paralysis. * **Option D:** Under the Universal Immunization Programme (UIP) and Pulse Polio Immunization (PPI), OPV is administered to children up to **5 years of age**. **High-Yield Clinical Pearls for NEET-PG:** * **Agent:** RNA Enterovirus (Poliovirus Type 1 is most commonly associated with paralytic outbreaks). * **Transmission:** Fecal-oral route is the most common in developing countries. * **Clinical Sign:** "Tripod Sign" (child sits with hands behind for support due to spinal rigidity). * **Vaccine:** **Sabin (OPV)** is a live attenuated vaccine (induces local IgA immunity); **Salk (IPV)** is an inactivated vaccine (induces humoral IgG immunity). * **Eradication:** India was declared Polio-free by the WHO on March 27, 2014.

Q: A healthcare worker sustains a needle-prick injury from a patient with HIV. What is the immediate management or treatment required?

Antiretroviral therapy. ### Explanation **Correct Answer: B. Antiretroviral therapy** The immediate management of a needle-stick injury (NSI) involving a known HIV-positive source is the initiation of **Post-Exposure Prophylaxis (PEP)** using Antiretroviral Therapy (ART). The goal is to inhibit viral replication before the virus can establish a systemic infection. According to NACO guidelines, PEP should be started as soon as possible—ideally within **2 hours** and no later than **72 hours**—and continued for **28 days**. **Analysis of Incorrect Options:** * **A & C (Vaccination):** There is currently no effective prophylactic vaccine available for HIV. Vaccination is a standard protocol for Hepatitis B post-exposure, but not for HIV. * **D (HIV testing):** While baseline testing of the healthcare worker (HCW) is mandatory to establish their pre-exposure status, it is a diagnostic step, not a "treatment" or "management" to prevent infection. Treatment (ART) must not be delayed while waiting for test results. **High-Yield Clinical Pearls for NEET-PG:** * **The "Golden Period":** PEP is most effective if started within 2 hours of exposure. * **Standard PEP Regimen (NACO):** A 3-drug regimen is now preferred: **Tenofovir (300mg) + Lamivudine (300mg) + Dolutegravir (50mg)** once daily for 28 days. * **Immediate First Aid:** Wash the site with soap and water. **Do not scrub** or use antiseptics like bleach; **do not squeeze** the wound to induce bleeding. * **Risk of Transmission:** The average risk of HIV transmission after a percutaneous exposure to HIV-infected blood is approximately **0.3%**. (Compare this to Hepatitis B, which is 6–30%, and Hepatitis C, which is ~1.8%).

Q: Which of the following are measures taken in Guinea worm prophylaxis, EXCEPT?

Mass treatment with Mebendazole. **Explanation:** The correct answer is **D. Mass treatment with Mebendazole**. Guinea worm disease (*Dracunculiasis*) is unique because there is **no effective vaccine or specific curative medicine** available to prevent or treat the infection. While Mebendazole has been trialed to facilitate the easier extraction of the worm by reducing inflammation, it does not prevent infection or act as a mass prophylactic agent. **Why the other options are incorrect (Measures for Prophylaxis):** * **Safe drinking water:** This is the cornerstone of prevention. Since the disease is transmitted by drinking water containing infected *Cyclops* (water fleas), providing piped water, borehole wells, or using fine-mesh cloth filters (0.15mm) effectively interrupts transmission. * **Control of Cyclops:** Biological or chemical control of the intermediate host is vital. Chemical treatment of stagnant water sources with **Temephos (Abate)** kills *Cyclops* without making the water unsafe for human consumption. * **Health education:** Educating the community to prevent infected individuals from wading into drinking water sources (which triggers the release of larvae) is essential to break the life cycle. **High-Yield Clinical Pearls for NEET-PG:** * **Eradication Status:** India was declared Guinea worm-free by the WHO in **February 2000**. The last case in India was reported in July 1996 (Rajasthan). * **Agent:** *Dracunculus medinensis* (the "fiery serpent"). * **Intermediate Host:** *Cyclops* (also known as the "water flea"). * **Incubation Period:** Approximately **1 year** (8–14 months). * **Diagnosis:** Typically made clinically by observing the worm emerging from a painful skin ulcer, usually on the lower limbs.

Q: Which of the following is NOT transmitted by the fecal-oral route?

Dracunculiasis (Guinea worm disease). ### Explanation The fecal-oral route involves the ingestion of water or food contaminated by the feces of an infected person. While many enteric pathogens follow this path, **Dracunculiasis (Guinea worm disease)** has a distinct mechanism of transmission. **1. Why Dracunculiasis is the Correct Answer:** Dracunculiasis is transmitted via the **cyclops-water route**, not the fecal-oral route. Infection occurs when a person drinks stagnant water containing **Cyclops** (water fleas) that are infected with L3 larvae of *Dracunculus medinensis*. The larvae are released from the skin of an infected human host directly into the water when they emerge through a painful blister; they do not pass through feces. **2. Analysis of Incorrect Options:** * **Poliovirus:** Primarily transmitted via the fecal-oral route (especially in areas with poor sanitation), though oropharyngeal secretions can also play a role in the early stages. * **Typhoid Fever:** Caused by *Salmonella typhi*, it is a classic example of a water-borne and food-borne disease transmitted through the ingestion of contaminated feces or urine (fecal-oral/urino-oral). * **Ascaris lumbricoides:** This soil-transmitted helminth is acquired by ingesting embryonated eggs found in soil contaminated with human feces (fecal-oral). **3. NEET-PG High-Yield Pearls:** * **Dracunculiasis Status:** India was declared **Guinea worm-free** by the WHO in February 2000 (the last case was reported in July 1996 in Rajasthan). * **Intermediate Host:** The Cyclops (specifically *Mesocyclops*) is the essential intermediate host. * **Prevention:** The simplest preventive measure is filtering water through a fine mesh cloth or boiling it to kill the Cyclops. * **Common Fecal-Oral mnemonic:** Remember the "5 F's" of transmission: Flies, Fingers, Feces, Food, and Fluids.

Question 1

What caused the maximum damage to Napoleon's army during his march to Moscow?

Accepted Answer

Typhus

Answer

Plague

Answer

Diarrhea

Answer

Typhoid

Question 2

What is the quarantine period for yellow fever?

Accepted Answer

6 days

Answer

1 day

Answer

2 days

Answer

10 days

Question 3

What is true about poliomyelitis?

Accepted Answer

Increased muscular activity leads to increased paralysis.

Answer

Paralytic poliomyelitis is the most common form.

Answer

It causes spastic paralysis.

Answer

The oral polio vaccine is given only to children under 3 years of age.

Question 4

Which of the following diseases are transmitted from animals to humans (zoonosis)?

Accepted Answer

Rabies, Plague, HIV

Answer

Rabies, Plague, Measles

Answer

Japanese encephalitis, HIV, Plague

Answer

Rabies, Japanese encephalitis, HIV

Question 5

A healthcare worker sustains a needle-prick injury from a patient with HIV. What is the immediate management or treatment required?

Accepted Answer

Antiretroviral therapy

Answer

Prophylactic vaccination

Answer

Vaccination and antiretroviral therapy

Answer

HIV testing

Question 6

Which of the following are measures taken in Guinea worm prophylaxis, EXCEPT?

Accepted Answer

Mass treatment with Mebendazole

Answer

Safe drinking water

Answer

Control of Cyclops

Answer

Health education

Question 7

All of the following cause a false positive Mantoux test except?

Accepted Answer

HIV/AIDS

Answer

Prior BCG vaccine

Answer

Degraded tuberculin

Answer

Faulty technique of injection

Question 8

Isolation in a patient with Salmonellosis is done:

Accepted Answer

Till 3 stool tests are negative

Answer

Till fever subsides

Answer

Till Widal becomes negative

Answer

For 48 hours of Chloramphenicol treatment

Question 9

Sputum examination under TP is indicated in a patient presenting with which of the following symptoms?

Accepted Answer

Chest pain

Answer

Cough of 1-2 weeks duration

Answer

Persistent cough of 1-2 weeks duration

Answer

Hemoptysis

Question 10

Which of the following is NOT transmitted by the fecal-oral route?

Accepted Answer

Dracunculiasis (Guinea worm disease)

Answer

Poliovirus

Answer

Typhoid fever

Answer

Ascaris lumbricoides

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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