Infectious Diseases Practice Questions

Q: What is the incubation period of Nipah virus?

4-14 days. **Explanation:** The incubation period (IP) of **Nipah Virus (NiV)** typically ranges from **4 to 14 days**. However, it is important to note that incubation periods as long as 45 days have been reported in rare instances. **Why Option A is Correct:** According to the World Health Organization (WHO) and the CDC, the most common interval between exposure and symptom onset is 4–14 days. This period represents the time required for the virus to replicate sufficiently within the host’s respiratory or neurological systems to manifest clinical symptoms like fever, encephalitic syndrome, or respiratory distress. **Analysis of Incorrect Options:** * **Option B (2-6 days):** This is too short for Nipah but is characteristic of viruses like **Influenza** or **Ebola** (which has a broader range but often presents early). * **Option C (3-8 days):** This range is more typical for **Dengue fever** (3–14 days, commonly 4–7). * **Option D (5-10 days):** While overlapping with the Nipah range, it is too narrow and is more representative of the IP for **Leptospirosis** or certain Rickettsial infections. **High-Yield Clinical Pearls for NEET-PG:** * **Reservoir:** Fruit bats of the genus *Pteropus* (Flying foxes). * **Transmission:** Consumption of raw date palm sap contaminated with bat excreta, direct contact with infected pigs, or human-to-human transmission (especially in hospital settings). * **Clinical Hallmark:** Acute Encephalitis (high mortality rate: 40%–75%) and severe respiratory illness. * **Diagnosis:** RT-PCR (from throat swabs, CSF, or urine) and ELISA (IgG/IgM). * **Treatment:** Primarily supportive; **Ribavirin** has been used in some outbreaks, and monoclonal antibodies (m102.4) are under investigation.

Q: During a year, 100 cases of malaria were detected by a thick smear in a population of 100,000. What is the annual parasite index?

1 per 1000. ### Explanation **1. Understanding the Correct Answer (Option A)** The **Annual Parasite Index (API)** is a key epidemiological indicator used under the National Center for Vector Borne Diseases Control (NCVBDC) to measure the incidence of malaria in a community. It is defined as the number of confirmed malaria cases (positive slides) per 1000 population per year. The formula for API is: $$\text{API} = \frac{\text{Total number of positive slides for parasite in a year}}{\text{Total population under surveillance}} \times 1000$$ **Calculation:** * Total positive cases = 100 * Total population = 100,000 * $\text{API} = (100 / 100,000) \times 1000 = \mathbf{1 \text{ per } 1000}$ **2. Analysis of Incorrect Options** * **Option B (2 per 1000):** This would require 200 cases in the same population. * **Option C (10 per 1000):** This would require 1,000 cases in the same population. * **Option D (20 per 1000):** This would require 2,000 cases. This level often triggers intensified control measures (API > 2 is the threshold for indoor residual spray in many guidelines). **3. NEET-PG High-Yield Pearls** * **API vs. ABER:** While API measures disease burden, the **Annual Blood Examination Rate (ABER)** measures the efficiency of the surveillance system. A minimum ABER of **10%** is required for effective malaria monitoring. * **Slide Positivity Rate (SPR):** This is the percentage of slides examined that are positive for malaria. * **Thresholds:** An **API < 1** is often the target for moving from the "control" phase to the "elimination" phase in the National Framework for Malaria Elimination in India. * **Thick vs. Thin Smear:** Thick smears are used for **detection** (higher sensitivity), while thin smears are used for **species identification** and quantification.

Q: Sputum examination under DTP is indicated when a patient presents with which of the following?

Hemoptysis. **Explanation:** Under the **District Tuberculosis Programme (DTP)** and the current **National TB Elimination Programme (NTEP)** guidelines, the primary objective is the early identification of "Presumptive TB" cases. **Why Hemoptysis is the Correct Answer:** Hemoptysis (coughing up blood) is considered a "cardinal symptom" of pulmonary tuberculosis. According to the diagnostic algorithm, any individual presenting with hemoptysis—regardless of the duration of other symptoms—must undergo a sputum examination (Sputum Smear or NAAT/CBNAAT) to rule out active TB. It signifies potential parenchymal lung damage or cavitary disease, making it a high-priority clinical indicator. **Analysis of Incorrect Options:** * **Options A & B (Cough of 1-2 weeks):** Current NTEP guidelines define a "Presumptive TB" case as an individual with a **persistent cough for 2 weeks or more**. A cough of only 1 week, unless accompanied by other red flags like hemoptysis or significant weight loss, does not automatically trigger a sputum mandate under the standard screening protocol. * **Option D (Chest pain):** While chest pain can occur in TB (especially with pleural involvement), it is a non-specific symptom. On its own, without a persistent cough or hemoptysis, it is not a primary indication for sputum examination under the DTP. **High-Yield Clinical Pearls for NEET-PG:** * **Presumptive TB Definition:** Persistent cough ≥ 2 weeks, fever ≥ 2 weeks, significant weight loss, or **hemoptysis**. * **Diagnostic Gold Standard:** In the NTEP, **NAAT (CBNAAT/Truenat)** has replaced sputum microscopy as the initial diagnostic test where available. * **Sputum Collection:** Under the RNTCP/NTEP, two samples are required (one spot and one morning sample), though the focus has shifted toward rapid molecular diagnostics.

Q: When planning home care for a client with hepatitis A, which preventive measure should be emphasized to protect the client’s family?

Using good sanitation with dishes and shared bathrooms. **Explanation:** **1. Why Option B is Correct:** Hepatitis A Virus (HAV) is primarily transmitted via the **fecal-oral route**. In a home setting, the virus is shed in the feces of the infected individual. Transmission occurs through contaminated food, water, or fomites (shared objects). Therefore, the cornerstone of prevention is breaking the chain of transmission through **stringent personal hygiene and sanitation**. This includes meticulous handwashing, disinfecting shared bathrooms, and ensuring dishes are thoroughly cleaned to prevent cross-contamination among family members. **2. Why Other Options are Incorrect:** * **Option A:** Complete isolation is unnecessary. Standard enteric precautions are sufficient. Once jaundice appears, the period of peak infectivity has usually passed. * **Option C & D:** These measures are specific to **Hepatitis B, C, and D**, which are transmitted via parenteral (blood-borne) and sexual routes. While general hygiene is good practice, HAV is not typically spread through blood or needle sharing. **3. NEET-PG High-Yield Pearls:** * **Incubation Period:** 15–45 days (Average: 28 days). * **Infectivity:** Maximum during the late incubation period (2 weeks before the onset of jaundice) and decreases rapidly after jaundice appears. * **Diagnosis:** **Anti-HAV IgM** is the gold standard for acute infection; **Anti-HAV IgG** indicates past infection or immunity. * **Prophylaxis:** * **Active:** Inactivated HAV vaccine (2 doses, 6–12 months apart). * **Passive:** Immunoglobulin (0.02 mL/kg) given within 2 weeks of exposure. * **Complication:** HAV never leads to chronic hepatitis or a carrier state, unlike HBV or HCV. It can, however, rarely cause Fulminant Hepatic Failure.

Q: Which of the following is NOT a risk factor for gonococcal infection?

Age greater than 25 years. **Explanation:** The correct answer is **A. Age greater than 25 years**. **1. Why Option A is correct:** Gonococcal infection (*Neisseria gonorrhoeae*) is primarily a disease of the young. **Young age (specifically <25 years)** is a well-established risk factor. This is due to both behavioral factors (higher likelihood of new partners) and biological factors, such as **cervical ectopy** (the presence of columnar epithelium on the ectocervix), which is more common in younger women and more susceptible to infection by *N. gonorrhoeae* and *C. trachomatis*. Therefore, being older than 25 is considered a protective factor rather than a risk factor. **2. Why other options are incorrect:** * **B. Prior or current STDs:** A history of STDs indicates high-risk sexual behavior and potential mucosal damage, increasing the susceptibility to new infections. * **C. New or multiple sexual partners:** This increases the statistical probability of exposure to an infected individual, which is the primary driver of STD transmission. * **D. Lack of barrier protection:** Consistent use of condoms acts as a physical barrier against the transmission of infected secretions. Lack of such protection is a major risk factor for all bacterial STDs. **Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** Nucleic Acid Amplification Test (NAAT). * **Culture Medium:** Thayer-Martin Media (selective for *Neisseria*). * **Treatment:** Due to rising resistance, the current CDC recommendation is a single dose of **Ceftriaxone 500 mg IM**. If Chlamydia is not ruled out, add Doxycycline. * **Fitz-Hugh-Curtis Syndrome:** A complication of PID (often gonococcal) involving perihepatitis and "violin-string" adhesions.

Q: What is the risk of mother-to-child HIV transmission during delivery and after delivery in a non-breastfeeding woman?

15-30%. ### Explanation **1. Why Option B (15-30%) is Correct:** In the absence of any medical intervention (Antiretroviral Therapy or ART), the risk of Mother-to-Child Transmission (MTCT) of HIV is approximately **15-30%** in non-breastfeeding women. This transmission occurs primarily during two phases: **In-utero** (5-10%) and **Intrapartum/During delivery** (10-20%). The intrapartum period carries a higher risk due to the infant's exposure to infected maternal blood and vaginal secretions during labor. **2. Analysis of Incorrect Options:** * **Option A (5-10%):** This represents the risk of transmission specifically during the *antenatal* period (in-utero) only. It does not account for the significant risk during delivery. * **Option C (10-15%):** This is the additional risk attributed specifically to *breastfeeding* if the mother continues it for up to 24 months. If a woman breastfeeds, the total cumulative risk rises from 15-30% to approximately 35-45%. * **Option D (>50%):** This is incorrectly high. Even without intervention, more than half of the children born to HIV-positive mothers will not contract the virus. **3. High-Yield Clinical Pearls for NEET-PG:** * **Total Risk (No Intervention):** 15-30% (Non-breastfeeding) vs. 35-45% (Breastfeeding). * **Impact of ART:** With effective ART and undetectable viral load, the risk of MTCT can be reduced to **less than 1%**. * **PPTCT Protocol (India):** All pregnant women are screened for HIV. If positive, the mother is started on a lifelong **TLD regimen** (Tenofovir + Lamivudine + Dolutegravir) regardless of CD4 count. * **Infant Prophylaxis:** Nevirapine syrup is given to the infant for 6 weeks (can be extended to 12 weeks in high-risk cases). * **Diagnosis in Infants:** HIV DNA PCR is the gold standard (at 6 weeks); antibody tests (ELISA) are unreliable before 18 months due to persisting maternal antibodies.

Q: What is the best method for immunoprophylaxis of leprosy?

Killed ICRC bacillus. **Explanation:** The immunoprophylaxis of Leprosy involves the use of specific mycobacterial vaccines to stimulate cell-mediated immunity (CMI) against *Mycobacterium leprae*. **Why Killed ICRC Bacillus is Correct:** The **ICRC vaccine** (Indian Cancer Research Centre) is a first-generation vaccine derived from a cultivable mycobacterium belonging to the *M. avium-intracellulare* group, isolated from human lepromata. It shares significant antigenic determinants with *M. leprae*. Clinical trials in India have demonstrated that it provides significant protection and induces lepromin conversion in lepromatous leprosy patients and their contacts. Other vaccines used in leprosy include the **Mycobacterium w (Mw)** vaccine (now known as Leprovac) and the BCG vaccine (which offers variable protection). **Analysis of Incorrect Options:** * **A. MMR vaccine:** This is a live attenuated vaccine used for Measles, Mumps, and Rubella. It has no antigenic similarity to mycobacteria and provides no protection against leprosy. * **C. Plague bacillus vaccine:** This is used for *Yersinia pestis*. It is a killed vaccine (though newer versions exist) and is unrelated to leprosy prophylaxis. * **D. Anthrax bacillus vaccine:** This is used for *Bacillus anthracis*, primarily for high-risk individuals (veterinarians/military). It has no role in mycobacterial immunity. **High-Yield Pearls for NEET-PG:** * **BCG Vaccine:** While primarily for TB, BCG offers 20-40% protection against leprosy. Adding killed *M. leprae* to BCG increases its efficacy. * **Mycobacterium w (Mw):** Developed in India by Dr. G.P. Talwar; it is used as an immunotherapeutic adjunct to MDT. * **Chemoprophylaxis:** The current WHO recommendation for contacts of leprosy patients is a **Single Dose of Rifampicin (SDR)**. * **Most common site of leprosy:** Skin and peripheral nerves.

Q: Pleomorphism is seen in which of the following conditions?

Chickenpox. **Explanation:** **Pleomorphism** is a hallmark clinical feature of **Chickenpox** (caused by the Varicella-Zoster virus). In this context, pleomorphism refers to the simultaneous presence of skin lesions at **different stages of development** in the same anatomical area. Within a single cluster, one can observe macules, papules, vesicles ("dewdrops on a rose petal"), and crusts/scabs. This occurs because the rash appears in successive crops over 3–5 days. **Analysis of Options:** * **A. Chickenpox (Correct):** Characterized by a rapid progression of lesions, centripetal distribution (more on the trunk), and distinct pleomorphism. * **B. Rubella:** Presents with a discrete maculopapular rash that starts on the face and spreads downwards (cephalocaudal). It disappears in the order it appeared and does not show pleomorphism. * **C. Smallpox:** Unlike chickenpox, smallpox lesions are **monomorphic**. This means all lesions in a particular area are at the same stage of development. The rash is centrifugal (more on extremities) and lesions are deep-seated. * **D. Toxocara:** A parasitic infection (Visceral Larva Migrans) that typically presents with eosinophilia, hepatomegaly, or ocular involvement, but not a pleomorphic vesicular rash. **High-Yield Clinical Pearls for NEET-PG:** * **Distribution:** Chickenpox is **centripetal** (trunk > face > limbs); Smallpox is **centrifugal** (limbs/face > trunk). * **Axilla:** Chickenpox characteristically involves the axilla; Smallpox typically spares it. * **Scabs:** In Chickenpox, scabs begin to form 4–7 days after the rash appears and are **not infectious**. * **Incubation Period:** Chickenpox is usually 14–16 days (Range: 10–21 days). * **Secondary Attack Rate (SAR):** Very high for Chickenpox (approx. 90%), making it highly contagious.

Question 1

What is the incubation period of Nipah virus?

Accepted Answer

4-14 days

Answer

2-6 days

Answer

3-8 days

Answer

5-10 days

Question 2

During a year, 100 cases of malaria were detected by a thick smear in a population of 100,000. What is the annual parasite index?

Accepted Answer

1 per 1000

Answer

2 per 1000

Answer

10 per 1000

Answer

20 per 1000

Question 3

Sputum examination under DTP is indicated when a patient presents with which of the following?

Accepted Answer

Hemoptysis

Answer

Cough of 1-2 weeks duration

Answer

Persistent cough of 1-2 weeks duration

Answer

Chest pain

Question 4

When planning home care for a client with hepatitis A, which preventive measure should be emphasized to protect the client’s family?

Accepted Answer

Using good sanitation with dishes and shared bathrooms

Answer

Keeping the client in complete isolation

Answer

Avoiding contact with blood-soiled clothing or dressings

Answer

Forbidding the sharing of needles or syringes

Question 5

Which of the following drugs is administered unsupervised as per National Health Programmes?

Accepted Answer

Dapsone

Answer

Rifampicin

Answer

Ethambutol

Answer

Clofazimine

Question 6

What is the number of holes per square inch of a standard mosquito net?

Accepted Answer

150

Answer

100

Answer

250

Answer

175

Question 7

Which of the following is NOT a risk factor for gonococcal infection?

Accepted Answer

Age greater than 25 years

Answer

Prior or current sexually transmitted diseases

Answer

New or multiple sexual partners

Answer

Lack of barrier modes of protection

Question 8

What is the risk of mother-to-child HIV transmission during delivery and after delivery in a non-breastfeeding woman?

Accepted Answer

15-30%

Answer

5-10%

Answer

10-15%

Answer

More than 50%

Question 9

What is the best method for immunoprophylaxis of leprosy?

Accepted Answer

Killed ICRC bacillus

Answer

MMR vaccine

Answer

Plague bacillus vaccine

Answer

Anthrax bacillus vaccine

Question 10

Pleomorphism is seen in which of the following conditions?

Accepted Answer

Chickenpox

Answer

Rubella

Answer

Smallpox

Answer

Toxocara

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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