Infectious Diseases Practice Questions

Q: A 40-year-old man returns from rural Cambodia with fever and severe thrombocytopenia (platelet count 15,000/μL). Peripheral smear shows ring forms with multiple infections per RBC and appliqué forms. Rapid diagnostic test is positive for Plasmodium falciparum HRP2. What is the most appropriate first-line treatment?

Intravenous artesunate. ***Intravenous artesunate*** - This patient presents with **severe malaria** criteria, indicated by a very low platelet count and high-density **Plasmodium falciparum** infection with characteristic **appliqué forms** and multiple ring forms per RBC [1]. - **Intravenous artesunate** is the drug of choice for severe malaria globally as it reduces mortality more effectively than quinine, even in Southeast Asian regions with emerging resistance [1]. *Oral artemether-lumefantrine* - While effective for **uncomplicated malaria**, oral medications are inappropriate for cases showing signs of severity like **severe thrombocytopenia** or high parasitemia [2]. - Patients with severe malaria require parenteral therapy to ensure rapid drug levels and because they may not tolerate oral intake [1]. *Chloroquine with primaquine* - This combination is ineffective here because **Plasmodium falciparum** in Cambodia is highly resistant to **chloroquine** [3]. - **Primaquine** is primarily used to eradicate **hypnozoites** in P. vivax and P. ovale infections, which are not the cause of this patient's acute severe presentation [2]. *Intravenous quinine with doxycycline* - **Intravenous quinine** was previously the standard of care but has been superseded by artesunate due to its higher toxicity and inferior survival outcomes [1]. - Quinine is associated with significant side effects such as **cinchonism** and **hypoglycemia**, making it a second-line option when artesunate is unavailable [2].

Q: A 42-year-old man presents with fever, severe joint pains in small joints of hands and feet, and maculopapular rash for 5 days. He returned from Caribbean islands 10 days ago. RT-PCR confirms alphavirus infection. What is the most appropriate management?

Supportive care with NSAIDs and rest. ***Supportive care with NSAIDs and rest*** - The patient presents with classic symptoms of **Chikungunya fever**, an **alphavirus** infection characterized by high fever, **maculopapular rash**, and severe, often debilitating polyarthralgia. - There is no specific **antiviral therapy** for Chikungunya; management relies on **supportive care** including **NSAIDs**, hydration, and rest to manage pain and inflammation. *Start oseltamivir therapy* - **Oseltamivir** is a neuraminidase inhibitor used specifically for the treatment and prophylaxis of **Influenza A and B**. - It has no clinical utility or mechanism of action against **alphaviruses** like Chikungunya. *Start ribavirin immediately* - **Ribavirin** is a broad-spectrum antiviral used for conditions like **Hepatitis C** or **Lassa fever**, but it is not indicated for Chikungunya. - Clinical studies have not demonstrated a significant therapeutic benefit for using **ribavirin** in acute **alphavirus** infections. *Intravenous immunoglobulin* - **IVIG** is typically reserved for severe **immunomodulatory diseases** or specific complications like Guillain-Barré syndrome. - It is not a standard or recommended treatment for the acute phase of **Chikungunya fever** and does not replace standard supportive measures.

Q: Which of the following statements regarding Pneumocystis jirovecii pneumonia (PCP) is/are true? 1. Bronchoscopy with bronchoalveolar lavage (BAL) is the mainstay of diagnosis for PCP. 2. Pneumatoceles are seen in all cases of PCP. 3. A CD4 count < 350 cells/µL is an indication for prophylaxis against PCP. 4. Trimethoprim-sulfamethoxazole is the drug of choice for prophylaxis.

1 - True, 2 - False, 3 - False, 4 - True. **Explanation:** **1. Bronchoscopy with BAL is the mainstay of diagnosis (True):** *Pneumocystis jirovecii* cannot be cultured. Diagnosis relies on microscopic visualization of cysts or trophic forms in respiratory specimens [1]. While induced sputum is the initial non-invasive step, **Bronchoalveolar Lavage (BAL)** is the gold standard diagnostic procedure due to its high sensitivity (>90-95%) [1]. **2. Pneumatoceles are seen in all cases (False):** The classic radiological finding in PCP is **bilateral diffuse ground-glass opacities** (perihilar distribution). While pneumatoceles (thin-walled air-filled cysts) can occur and increase the risk of spontaneous pneumothorax, they are seen in only about 10-20% of cases, not all [1]. **3. CD4 count < 350 cells/µL is the indication for prophylaxis (False):** In HIV-infected patients, primary prophylaxis for PCP is indicated when the **CD4 count falls below 200 cells/µL** (or if there is a history of oropharyngeal candidiasis) [1]. A threshold of 350 cells/µL is too high for initiating PCP-specific prophylaxis. **4. Trimethoprim-sulfamethoxazole (TMP-SMX) is the drug of choice (True):** TMP-SMX is the first-line agent for both the **treatment and prophylaxis** of PCP [1]. It is highly effective and also provides cross-protection against Toxoplasmosis. **High-Yield Clinical Pearls for NEET-PG:** * **Stains:** Use **Gomori Methenamine Silver (GMS)** to see crushed-ping-pong-ball shaped cysts or **Giemsa** for trophic forms [1]. * **Biomarker:** Elevated **Serum Beta-D-Glucan** has high sensitivity (negative predictive value) for PCP [2]. * **Steroids:** Indicated in treatment if **PaO2 35 mmHg to prevent inflammatory worsening [1]. * **Alternative for Prophylaxis:** Dapsone or Atovaquone (if sulfa-allergic) [1].

Q: The tourniquet test is used for monitoring patients with which of the following conditions?

Dengue fever. **Explanation:** The **Tourniquet Test** (Hess test) is a clinical diagnostic tool used to assess **capillary fragility** and is a key component of the WHO criteria for diagnosing **Dengue Fever**. [1] **Why Dengue Fever is correct:** In Dengue, the virus causes increased vascular permeability and thrombocytopenia. The test is performed by inflating a blood pressure cuff to a point midway between the systolic and diastolic pressure for 5 minutes. [1] A positive test is defined as the presence of **≥10 to 20 petechiae per square inch**. It serves as a marker for potential hemorrhagic manifestations and is often positive before the platelet count drops significantly. [1] **Why other options are incorrect:** * **Infectious Mononucleosis:** Caused by EBV; characterized by the triad of fever, pharyngitis, and lymphadenopathy. Diagnosis relies on the Monospot test or atypical lymphocytes on a peripheral smear. * **Zika Virus:** Primarily presents with a maculopapular rash, conjunctivitis, and arthralgia. While it is a Flavivirus like Dengue, capillary fragility is not a hallmark feature. * **Chikungunya:** An Alphavirus characterized by severe, often debilitating polyarthralgia. While it shares the vector (*Aedes*) with Dengue, it does not typically cause the capillary leak syndrome associated with a positive tourniquet test. **Clinical Pearls for NEET-PG:** * **Sensitivity:** The tourniquet test has high specificity but variable sensitivity; a negative test does **not** rule out Dengue. * **Dengue Triad:** High-grade fever, retro-orbital pain, and severe backache ("Break-bone fever"). * **Critical Phase:** Watch for "Warning Signs" (abdominal pain, persistent vomiting, mucosal bleed) which usually occur during the transition from the febrile to the afebrile phase (defervescence). [1]

Q: What is the recommended dose of tetanus toxoid to prevent maternal and neonatal tetanus for a pregnant woman whose previous immunization status is not known?

2 doses. **Explanation:** The primary goal of tetanus immunization during pregnancy is to prevent maternal tetanus and provide passive immunity to the fetus to prevent neonatal tetanus. **Why Option B is Correct:** According to the National Immunization Schedule (NIS) and WHO guidelines, if a pregnant woman’s immunization status is unknown or she has never been vaccinated, she should receive **two doses** of the tetanus vaccine (currently administered as Tetanus and adult Diphtheria, or **Td** vaccine). * **First Dose:** Administered as early as possible during pregnancy. * **Second Dose:** Administered at least **4 weeks** after the first dose and preferably at least 2 weeks before delivery to ensure adequate antibody transfer. **Why Other Options are Incorrect:** * **Option A (1 dose):** A single dose is insufficient to produce a protective level of antibodies in a previously unimmunized individual. A single "booster" dose is only appropriate if the woman has received at least 2 doses in a pregnancy within the last 3 years. * **Options C & D (3 or 4 doses):** While the full WHO "Life-course" schedule for tetanus involves 5–6 doses for long-term protection, the standard protocol *during a single pregnancy* to ensure immediate protection of the neonate is 2 doses. **High-Yield Clinical Pearls for NEET-PG:** * **The "Booster" Rule:** If a woman becomes pregnant again within **3 years** of receiving two doses, only **one booster dose** (Td) is required. * **Vaccine Type:** The Td vaccine has replaced TT (Tetanus Toxoid) to provide additional protection against adult diphtheria. * **Site/Route:** 0.5 ml, Intramuscular (IM), usually in the upper arm (deltoid). * **Neonatal Tetanus:** Also known as "8th-day disease," it typically presents with trismus (lockjaw) and spasms due to umbilical cord contamination.

Q: In Human Immunodeficiency Virus (HIV) infection, diffuse lymphadenopathy in a person who is clinically well is usually a sign of which of the following?

Persistent generalized lymphadenopathy. The correct answer is **Persistent Generalized Lymphadenopathy (PGL)**. **1. Why PGL is correct:** PGL is defined as enlarged lymph nodes (>1 cm) involving at least two extra-inguinal sites for more than 3 to 6 months, without an obvious underlying cause other than HIV. It is a hallmark of the **early clinical stage (WHO Stage 1)** of HIV infection [1]. Pathologically, it represents follicular hyperplasia in response to the virus. Crucially, patients with PGL are typically **asymptomatic ("clinically well")** except for the lymphadenopathy [1]. **2. Why the other options are incorrect:** * **Lymphoma (A):** While HIV increases the risk of Non-Hodgkin Lymphoma, patients usually present with systemic "B symptoms" (fever, weight loss, night sweats) and rapid nodal growth [2]. It signifies an advanced stage, not a "clinically well" state. * **Kaposi’s Sarcoma (B):** This is an AIDS-defining illness (WHO Stage 4). While it can involve lymph nodes, it primarily presents with characteristic violaceous skin or mucosal lesions. * **Tuberculosis (C):** TB is the most common opportunistic infection in HIV patients in India. However, TB lymphadenitis (Scrofula) usually presents with constitutional symptoms (fever, weight loss), and the nodes are often matted or suppurative, unlike the discrete, non-tender nodes of PGL [2]. **Clinical Pearls for NEET-PG:** * **PGL Node Characteristics:** Typically non-tender, symmetrical, firm, and mobile. Common sites include cervical, axillary, and posterior occipital nodes. * **Biopsy Indication:** Biopsy in PGL is **not** routinely required unless the patient has systemic symptoms, asymmetric nodal enlargement, or nodes that rapidly increase in size [2]. * **WHO Staging:** PGL is classified under **WHO Clinical Stage 1** [1].

Q: The most severe form of respiratory complication in influenza virus infection is:

Primary viral pneumonia. **Explanation:** **Primary viral pneumonia** is the most severe and least common respiratory complication of influenza [1]. It typically occurs in high-risk groups (e.g., patients with mitral stenosis or pregnancy). It is characterized by rapid progression of fever, dyspnea, and cyanosis within 24–48 hours of flu onset. Pathologically, it causes diffuse interstitial inflammation, alveolar hemorrhage, and edema, often leading to Acute Respiratory Distress Syndrome (ARDS) and high mortality rates. **Analysis of Incorrect Options:** * **Secondary bacterial pneumonia:** While more common than primary viral pneumonia, it is usually less severe [1]. It typically presents as a "biphasic illness" where the patient improves then worsens. *S. pneumoniae* is the most common cause, but *S. aureus* is the most serious secondary invader [2]. * **Acute pneumatocele:** These are thin-walled, air-filled cysts typically associated with *Staphylococcus aureus* pneumonia. While serious, they are a localized complication rather than a systemic respiratory failure. * **Bilateral pleural effusion:** While effusions can occur in severe pneumonia, they are usually reactive (parapneumonic) and do not represent the primary life-threatening mechanism of the influenza virus itself. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication of Influenza:** Secondary bacterial pneumonia [1]. * **Most common organism in secondary pneumonia:** *Streptococcus pneumoniae* [2]. * **Most concerning organism in secondary pneumonia:** *Staphylococcus aureus* (often MRSA, causing necrotizing pneumonia) [2]. * **Radiology:** Primary viral pneumonia shows diffuse interstitial infiltrates; secondary bacterial pneumonia shows focal lobar consolidation. * **Drug of Choice:** Oseltamivir (Neuraminidase inhibitor), most effective if started within 48 hours.

Q: What is the percentage of coincidence between a sore throat and acute rheumatic fever?

3%. ### Explanation **1. Understanding the Correct Answer (Option A: 3%)** Acute Rheumatic Fever (ARF) is a nonsuppurative inflammatory complication that follows a Group A Streptococcal (GAS) pharyngitis. Epidemiological studies conducted in the mid-20th century (notably at Warren Air Force Base) established that approximately **3% of individuals** with untreated or inadequately treated exudative streptococcal sore throats will develop ARF. This "3% rule" applies specifically to epidemic situations [1]. In endemic settings or during sporadic outbreaks, the attack rate can be significantly lower (often <1.0%), but for standardized examinations like NEET-PG, 3% is the classic, high-yield figure. **2. Analysis of Incorrect Options** * **Option B (5%):** This overestimates the incidence. While GAS is common, the host immune response required to trigger ARF is specific and occurs in a minority of the population. * **Options C & D (7% and 9%):** These figures are significantly higher than documented clinical data. Even in the absence of antibiotics, the vast majority of patients with a sore throat do not develop the systemic autoimmune response characteristic of ARF. **3. Clinical Pearls for NEET-PG** * **The Latent Period:** ARF typically develops **1–5 weeks** (average 3 weeks) after the initial sore throat. * **Prevention:** Primary prevention of ARF involves treating GAS pharyngitis with a single dose of Benzathine Penicillin G or a 10-day course of oral Penicillin V [1]. * **Jones Criteria:** Diagnosis is clinical, based on the Revised Jones Criteria (Major: Carditis, Polyarthritis, Chorea, Erythema Marginatum, Subcutaneous nodules) [1]. * **Site Specificity:** Note that ARF follows **pharyngeal** infections only, whereas Post-Streptococcal Glomerulonephritis (PSGN) can follow either pharyngeal or skin (impetigo) infections.

Question 1

A 40-year-old man returns from rural Cambodia with fever and severe thrombocytopenia (platelet count 15,000/μL). Peripheral smear shows ring forms with multiple infections per RBC and appliqué forms. Rapid diagnostic test is positive for Plasmodium falciparum HRP2. What is the most appropriate first-line treatment?

Accepted Answer

Intravenous artesunate

Answer

Oral artemether-lumefantrine

Answer

Chloroquine with primaquine

Answer

Intravenous quinine with doxycycline

Question 2

A 42-year-old man presents with fever, severe joint pains in small joints of hands and feet, and maculopapular rash for 5 days. He returned from Caribbean islands 10 days ago. RT-PCR confirms alphavirus infection. What is the most appropriate management?

Accepted Answer

Supportive care with NSAIDs and rest

Answer

Start oseltamivir therapy

Answer

Start ribavirin immediately

Answer

Intravenous immunoglobulin

Question 3

A rash appeared 9 hours after a scuba dive. What is the diagnosis?

Accepted Answer

Decompression sickness

Answer

Jellyfish envenomation

Answer

Mycobacterium marinum infection

Answer

Phylum Porifera contact dermatitis

Question 4

Which of the following statements regarding Pneumocystis jirovecii pneumonia (PCP) is/are true? 1. Bronchoscopy with bronchoalveolar lavage (BAL) is the mainstay of diagnosis for PCP. 2. Pneumatoceles are seen in all cases of PCP. 3. A CD4 count < 350 cells/µL is an indication for prophylaxis against PCP. 4. Trimethoprim-sulfamethoxazole is the drug of choice for prophylaxis.

Accepted Answer

1 - True, 2 - False, 3 - False, 4 - True

Answer

1 - False, 2 - True, 3 - True, 4 - False

Answer

1 - True, 2 - True, 3 - False, 4 - True

Answer

1 - False, 2 - False, 3 - True, 4 - False

Question 5

The tourniquet test is used for monitoring patients with which of the following conditions?

Accepted Answer

Dengue fever

Answer

Infectious mononucleosis

Answer

Zika Virus infection

Answer

Chikungunya

Question 6

What is the recommended dose of tetanus toxoid to prevent maternal and neonatal tetanus for a pregnant woman whose previous immunization status is not known?

Accepted Answer

2 doses

Answer

1 dose

Answer

3 doses

Answer

4 doses

Question 7

In a person with HIV-1 infection, which of the following is the most predictive of the patient's prognosis?

Accepted Answer

Level of HIV-1 RNA in plasma

Answer

CD4+ cell count

Answer

CD4:CD8 cell ratio

Answer

Degree of lymphadenopathy

Question 8

In Human Immunodeficiency Virus (HIV) infection, diffuse lymphadenopathy in a person who is clinically well is usually a sign of which of the following?

Accepted Answer

Persistent generalized lymphadenopathy

Answer

Lymphoma

Answer

Kaposi's sarcoma

Answer

Tuberculosis

Question 9

The most severe form of respiratory complication in influenza virus infection is:

Accepted Answer

Primary viral pneumonia

Answer

Secondary pseudomonal pneumonia

Answer

Acute pneumatocele

Answer

Bilateral pleural effusion

Question 10

What is the percentage of coincidence between a sore throat and acute rheumatic fever?

Accepted Answer

3%

Answer

5%

Answer

7%

Answer

9%

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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