A 19-year-old engineering student has fever, severe sore throat with tonsillar exudate, tender posterior cervical nodes and a palpable spleen. He took amoxicillin from a local clinic and developed a generalised itchy maculopapular rash. TLC is 14,000/µL with 60% lymphocytes, many large with abundant cytoplasm indenting around red cells. What are these large cells?

Activated CD8+ cytotoxic T cells

Immature lymphoblasts from marrow

Virus-infected circulating B cells

Reactive monocytes and macrophages

A 62-year-old man develops a painful band of grouped vesicles along the left T6 dermatome. He had chickenpox as a child. Where had the virus persisted during the intervening years?

Sensory neurons of the dorsal root ganglion

Circulating memory B lymphocytes

Endothelial cells lining the dermal capillaries

A 40-year-old man bitten on the leg by a stray dog receives wound washing, vaccine and rabies immunoglobulin, and remains well. Which feature of rabies virus pathogenesis explains why treatment given after the bite can still prevent disease?

The virus travels slowly along peripheral nerves with no viraemia

The virus circulates in blood for weeks before entering the brain

The virus replicates first in regional lymph nodes

The virus remains latent in the skin for years

A 70-year-old man with COPD is brought to casualty during influenza season with two days of fever, dry cough and increasing breathlessness; SpO2 is 92% on room air. A nasopharyngeal swab has been sent for influenza RT-PCR, and the result will take about 18 hours. What is the next best step for this patient?

Start oseltamivir now without waiting for the result

Wait for the RT-PCR result before any antiviral

Start azithromycin alone and review in 48 hours

Give a single dose of inactivated influenza vaccine now

Respiratory, arboviruses and other viruses

26 NEET-PG practice questions on Respiratory, arboviruses and other viruses, part of Microbiology. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
A 19-year-old engineering student has fever, severe sore throat with tonsillar exudate, tender posterior cervical nodes and a palpable spleen. He took amoxicillin from a local clinic and developed a generalised itchy maculopapular rash. TLC is 14,000/µL with 60% lymphocytes, many large with abundant cytoplasm indenting around red cells. What are these large cells?
1. AImmature lymphoblasts from marrow
2. BVirus-infected circulating B cells
3. CActivated CD8+ cytotoxic T cells
4. DReactive monocytes and macrophages
Show answerHide answer
Answer: C · Activated CD8+ cytotoxic T cells
Fever, exudative pharyngitis, posterior cervical nodes, splenomegaly and a rash after amoxicillin suggest infectious mononucleosis from Epstein-Barr virus. EBV infects B cells through CD21, and the atypical (Downey) lymphocytes in the blood are mainly activated CD8+ cytotoxic T cells responding to those infected B cells. The heterophile antibody (Paul-Bunnell or monospot) test or EBV VCA IgM confirms it. He should avoid contact sports for some weeks because the enlarged spleen can rupture, and the rash is not a true penicillin allergy.
- A: Blasts would suggest acute leukaemia; these cells are mature reactive lymphocytes.
- B: Infected B cells are few in the blood; the atypical cells are the T cells reacting to them.
- D: Monocytes do not account for the lymphocytosis; the cells are lymphocytes.
Question 2 · Easy
A 62-year-old man develops a painful band of grouped vesicles along the left T6 dermatome. He had chickenpox as a child. Where had the virus persisted during the intervening years?
1. ASensory neurons of the dorsal root ganglion
2. BCirculating memory B lymphocytes
3. CBasal cells of the epidermis
4. DEndothelial cells lining the dermal capillaries
Show answerHide answer
Answer: A · Sensory neurons of the dorsal root ganglion
After chickenpox, varicella-zoster virus travels along sensory nerves and establishes lifelong latency in the neurons of dorsal root and cranial nerve ganglia, with almost no gene expression. When cell-mediated immunity falls with age, immunosuppression or illness, the virus reactivates, travels back down the sensory nerve and produces vesicles limited to that dermatome, with pain that may precede the rash. Post-herpetic neuralgia is the commonest sequel, and antiviral treatment started early reduces the duration of the eruption.
- B: Latency is in neurons, not in B cells; memory B cells carry antibody responses, not the genome.
- C: Epidermal basal cells support the vesicular eruption but do not harbour latent virus.
- D: Dermal endothelium is not a site of varicella-zoster latency.
Question 3 · Medium
A 40-year-old man bitten on the leg by a stray dog receives wound washing, vaccine and rabies immunoglobulin, and remains well. Which feature of rabies virus pathogenesis explains why treatment given after the bite can still prevent disease?
1. AThe virus circulates in blood for weeks before entering the brain
2. BThe virus replicates first in regional lymph nodes
3. CThe virus travels slowly along peripheral nerves with no viraemia
4. DThe virus remains latent in the skin for years
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Answer: C · The virus travels slowly along peripheral nerves with no viraemia
After inoculation the rabies virus may replicate in local muscle, then enters peripheral nerve endings and moves centripetally up the axons to the spinal cord and brain. This journey takes weeks to months and there is no significant viraemia, so antibody from immunoglobulin at the wound and from the vaccine can neutralise virus before it reaches nerve tissue. That window is the whole basis of post-exposure prophylaxis. Once the virus reaches the central nervous system the disease is almost always fatal, and no treatment then alters the outcome.
- A: Rabies has no significant viraemic phase; spread is along nerves.
- B: Lymph node replication is not the route; the virus uses peripheral nerves.
- D: The virus does not lie latent in skin; the incubation period is the time of neural transit.
Question 4 · Medium
A 70-year-old man with COPD is brought to casualty during influenza season with two days of fever, dry cough and increasing breathlessness; SpO2 is 92% on room air. A nasopharyngeal swab has been sent for influenza RT-PCR, and the result will take about 18 hours. What is the next best step for this patient?
1. AWait for the RT-PCR result before any antiviral
2. BStart azithromycin alone and review in 48 hours
3. CStart oseltamivir now without waiting for the result
4. DGive a single dose of inactivated influenza vaccine now
Show answerHide answer
Answer: C · Start oseltamivir now without waiting for the result
Neuraminidase inhibitors work best when given early, and the benefit in high-risk patients is greatest within the first 48 hours of symptoms. An elderly man with COPD, hypoxia and an influenza-like illness in season should therefore be started on oseltamivir on clinical grounds and the drug stopped if the test is negative and another cause is found. Vaccination protects for future seasons and does nothing for an illness already under way. Antibiotics are added only if bacterial pneumonia is suspected.
- A: Waiting a day wastes the window in which antivirals reduce complications.
- B: An antibiotic alone leaves the viral infection untreated in a high-risk patient.
- D: Vaccine gives no immediate protection and is not treatment.
Question 5 · Easy
A 34-year-old woman in Bengaluru has abrupt high fever with severe, symmetrical pain and swelling of both wrists, ankles and the small joints of the hands, with a maculopapular rash. Several neighbours have had the same illness; dengue NS1 and malaria tests are negative. Which virus is most likely responsible?
1. AJapanese encephalitis virus
2. BChikungunya virus
3. CWest Nile virus
4. DZika virus
Show answerHide answer
Answer: B · Chikungunya virus
Chikungunya virus is an alphavirus of the family Togaviridae, spread by Aedes aegypti and Aedes albopictus, the same mosquitoes that carry dengue. Crippling, symmetrical polyarthralgia with fever and rash is its hallmark, and joint pain can persist for months after the fever settles. Mortality is low, and treatment is paracetamol with rest and fluids. Dengue must still be excluded because the two circulate together and dengue can kill through plasma leakage.
- A: Japanese encephalitis presents with encephalitis, not with symmetrical arthritis.
- C: West Nile virus causes fever with neuroinvasive disease, not disabling arthritis.
- D: Zika usually causes a mild rash and conjunctivitis; its main concern is fetal infection.
Question 6 · Medium
A 29-year-old man with no known illness is seen with painful vesicles involving two adjacent thoracic dermatomes on the right and a few scattered vesicles elsewhere. What is the most important next step along with antiviral treatment?
1. AScreen for diabetes with a fasting glucose only
2. BReassure and review after the rash heals
3. CStart oral corticosteroids
4. DOffer HIV testing with counselling
Answer and explanation in LearnFree account
Question 7 · Easy
Four people from one family in a Kozhikode village are admitted with fever, severe headache and rapidly worsening encephalitis; two have died. Nipah virus RNA is detected in their throat swabs. Which animal is the natural reservoir of this virus?
1. APigs reared in backyard farms
2. BField rodents in paddy fields
3. CPalm civets sold in live markets
4. DFruit bats of the genus Pteropus
Answer and explanation in LearnFree account
Question 8 · Hard
A medical officer reviewing a rabies death considers four statements: 1. Rabies virus is a bullet-shaped enveloped RNA virus. 2. Negri bodies are cytoplasmic inclusions seen in hippocampal pyramidal cells and cerebellar Purkinje cells. 3. Negri bodies are demonstrable in every confirmed human case. 4. A biting dog that stays healthy through ten days of observation makes rabies transmission from that bite unlikely. Which statements are correct?
1. A1 and 2 only
2. B1 and 3 only
3. C1, 2 and 4 only
4. D2 and 3 only
Answer and explanation in LearnFree account
Question 9 · Hard
A 9-year-old girl in Delhi had serologically confirmed dengue two years ago. She is now admitted on day 5 of a new febrile illness with abdominal pain, repeated vomiting, a rising haematocrit and platelets of 38,000/µL. Her father asks why this attack is more severe than the first. Which mechanism best explains the difference?
1. ANon-neutralising antibody increasing viral uptake by Fc receptors
2. BA larger inoculum of virus from the mosquito bite
3. CDirect lysis of platelets by the virus in the marrow
4. DLoss of protective immunity leaving her fully susceptible
Answer and explanation in LearnFree account
Question 10 · Medium
A 32-year-old nurse recovered from mild COVID-19 three weeks ago and completed her isolation. She is asymptomatic, but a repeat RT-PCR done for her own satisfaction is positive with a high cycle threshold value. How is this result best explained to her?
1. AResidual viral RNA can be detected after infectivity has ended
2. BThe laboratory has certainly made a technical error
3. CShe has been reinfected and must isolate for two more weeks
4. DInfectivity lasts as long as RT-PCR remains positive
Answer and explanation in LearnFree account
Question 11 · Medium
A 36-year-old man is six weeks past a live renal transplant and is on tacrolimus, mycophenolate and prednisolone. He has fever, malaise, a leucocyte count of 2,800/µL and platelets of 90,000/µL, with mildly raised transaminases and no localising signs. Which investigation is most useful to confirm the suspected infection?
1. AQuantitative CMV DNA PCR on blood
2. BBone marrow aspiration for storage cells
3. CUrine culture for bacteria
4. DCMV IgG on a single serum sample
Answer and explanation in LearnFree account
Question 12 · Easy
A 56-year-old man with diabetes is admitted with COVID-19 confirmed by RT-PCR. His son asks how the virus enters the cells of the lung. Which host molecule does the spike protein of SARS-CoV-2 bind?
1. ACD4 with the CCR5 co-receptor
2. BSialic acid residues on respiratory epithelium
3. CComplement receptor CD21
4. DAngiotensin-converting enzyme 2
Answer and explanation in LearnFree account
Question 13 · Hard
A 42-year-old man is admitted with four days of fever, confusion and two seizures. CSF shows 60 cells/µL with 90% lymphocytes, protein 85 mg/dL and glucose 62 mg/dL (blood 104 mg/dL). MRI shows swelling of the right temporal lobe with haemorrhagic change. Intravenous aciclovir was started on admission. The CSF herpes simplex virus PCR, sent on day 1 of admission, is negative. What is the next best step?
1. AChange to intravenous ganciclovir for suspected CMV
2. BContinue aciclovir and repeat the CSF PCR after 48 hours
3. CStop aciclovir, as the PCR has excluded herpes encephalitis
4. DStart antituberculous treatment with steroids
Answer and explanation in LearnFree account
Question 14 · Medium
A 38-year-old man from a district reporting Nipah cases is admitted with fever, myoclonus and falling consciousness. Which investigation best confirms the suspected infection in the acute stage?
1. AMRI brain with contrast and diffusion imaging
2. BElectroencephalography
3. CSerum IgG ELISA against Nipah virus
4. DReal-time RT-PCR on throat swab and CSF
Answer and explanation in LearnFree account
Question 15 · Medium
A 27-year-old woman at 20 weeks of pregnancy attends the antenatal clinic and asks about protection against influenza, as her sister was admitted with it last month. Which preparation is appropriate for her?
1. AOseltamivir taken daily through the season
2. BNo vaccine until after delivery
3. CInactivated influenza vaccine, given intramuscularly
4. DLive attenuated influenza vaccine, given intranasally
Answer and explanation in LearnFree account
Question 16 · Medium
A 31-year-old woman in Chennai has had fever and severe joint pain for two days during a chikungunya outbreak in her street. Which laboratory test is most likely to confirm chikungunya at this stage of her illness?
1. AIgG ELISA on serum
2. BIgM capture ELISA on serum
3. CReal-time RT-PCR on serum
4. DVirus isolation in suckling mice
Answer and explanation in LearnFree account
Question 17 · Medium
A 6-year-old boy with influenza-like illness is given aspirin by a neighbour for fever. Three days later he becomes drowsy and begins vomiting repeatedly; the liver is enlarged, transaminases are high and ammonia is raised, with no jaundice. Which complication has developed?
1. AParacetamol-induced hepatic necrosis
2. BDengue-associated liver failure
3. CReye syndrome
4. DAcute viral hepatitis A
Answer and explanation in LearnFree account
Question 18 · Hard
A 33-year-old healthy man with RT-PCR-confirmed COVID-19 has fever and cough for three days. He is comfortable at rest with a respiratory rate of 18/min and SpO2 of 98% on room air. He asks for a steroid injection and an antibiotic because a relative improved on them. What is the most appropriate response?
1. APrescribe azithromycin with oral steroids to prevent deterioration
2. BExplain that steroids help only when oxygen is needed, and treat symptoms
3. CAdmit him for intravenous steroids and monitoring
4. DGive oral dexamethasone for five days as he requests
Answer and explanation in LearnFree account
Question 19 · Medium
A 23-year-old woman attends the skin OPD with painful grouped vesicles and shallow ulcers on the vulva, appearing for the first time, with tender inguinal nodes and fever. A smear is taken from the base of a fresh vesicle and stained. Which finding supports the clinical diagnosis?
1. ADonovan bodies inside mononuclear cells
2. BMultinucleated giant cells with intranuclear inclusions
3. CClue cells with adherent coccobacilli
4. DGram-negative diplococci within neutrophils
Answer and explanation in LearnFree account
Question 20 · Hard
A 50-year-old man is admitted to a district hospital with hydrophobia, excessive salivation and episodes of terror, three months after an untreated dog bite. He is conscious between episodes. The family asks for every possible treatment. What is the most appropriate management?
1. AHigh-dose intravenous aciclovir and interferon
2. BIntensive care with therapeutic coma as standard treatment
3. CPalliative care with sedation and barrier nursing, after counselling the family
4. DRabies vaccine with immunoglobulin into the old wound site
Answer and explanation in LearnFree account
Question 21 · Medium
A 20-year-old man with dengue fever is on day 5 of illness. His haematocrit has risen from 39% to 48% and there is free fluid in the abdomen on ultrasound, while the serum albumin has fallen. What is the main mechanism of this fluid shift?
1. AA brief, reversible rise in capillary permeability
2. BReduced hepatic albumin synthesis from viral hepatitis
3. CImmune complex deposition causing fibrinoid necrosis of vessels
4. DDestruction of capillary endothelium by the virus
Answer and explanation in LearnFree account
Question 22 · Easy
A 29-year-old poultry farm worker in Haryana is admitted with fever and breathlessness during an outbreak of bird deaths on his farm. The reference laboratory reports an influenza A virus whose surface genes resemble an avian strain while its internal genes resemble a human strain. Which process explains the appearance of such a virus?
1. AAntigenic drift by point mutations in haemagglutinin
2. BPhenotypic mixing of two intact virions
3. CComplementation between two defective virions
4. DAntigenic shift by reassortment of gene segments
Answer and explanation in LearnFree account
Question 23 · Easy
A stray dog that bit three children in a Nagpur colony is killed the same day and its carcass is sent to the veterinary laboratory. Which test on the animal's brain is the standard method to confirm rabies?
1. AComplement fixation test on brain tissue
2. BTzanck smear of the brain impression
3. CHaemagglutination inhibition test on brain extract
4. DDirect fluorescent antibody test on brain smears
Answer and explanation in LearnFree account
Question 24 · Medium
During a Nipah outbreak, a medical officer in a Kerala district hospital must admit a patient with fever and encephalitis whose throat swab has been sent for Nipah RT-PCR. Which infection control measure is most appropriate while the result is awaited?
1. AOpen ward with a curtain and surgical masks for visitors only
2. BIsolation only after the RT-PCR report is positive
3. CStandard precautions alone, as spread needs mosquito bites
4. DSingle room with contact and airborne precautions for all staff
Answer and explanation in LearnFree account
Question 25 · Medium
A 45-year-old man in a Pune hospital has hydrophobia, aerophobia and agitation two months after a dog bite for which he took no treatment. The family wants laboratory confirmation. Which specimen and test is most appropriate while he is alive?
1. ASerum IgM on the day of admission
2. BRT-PCR on saliva and a nuchal skin biopsy
3. CBlood culture for the virus
4. DCSF protein and cell count
Answer and explanation in LearnFree account

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Respiratory, arboviruses and other viruses

A 62-year-old man develops a painful band of grouped vesicles along the left T6 dermatome. He had chickenpox as a child. Where had the virus persisted during the intervening years?

A 40-year-old man bitten on the leg by a stray dog receives wound washing, vaccine and rabies immunoglobulin, and remains well. Which feature of rabies virus pathogenesis explains why treatment given after the bite can still prevent disease?

A 29-year-old man with no known illness is seen with painful vesicles involving two adjacent thoracic dermatomes on the right and a few scattered vesicles elsewhere. What is the most important next step along with antiviral treatment?

Four people from one family in a Kozhikode village are admitted with fever, severe headache and rapidly worsening encephalitis; two have died. Nipah virus RNA is detected in their throat swabs. Which animal is the natural reservoir of this virus?

A 32-year-old nurse recovered from mild COVID-19 three weeks ago and completed her isolation. She is asymptomatic, but a repeat RT-PCR done for her own satisfaction is positive with a high cycle threshold value. How is this result best explained to her?

A 56-year-old man with diabetes is admitted with COVID-19 confirmed by RT-PCR. His son asks how the virus enters the cells of the lung. Which host molecule does the spike protein of SARS-CoV-2 bind?

A 38-year-old man from a district reporting Nipah cases is admitted with fever, myoclonus and falling consciousness. Which investigation best confirms the suspected infection in the acute stage?

A 27-year-old woman at 20 weeks of pregnancy attends the antenatal clinic and asks about protection against influenza, as her sister was admitted with it last month. Which preparation is appropriate for her?

A 31-year-old woman in Chennai has had fever and severe joint pain for two days during a chikungunya outbreak in her street. Which laboratory test is most likely to confirm chikungunya at this stage of her illness?

A 6-year-old boy with influenza-like illness is given aspirin by a neighbour for fever. Three days later he becomes drowsy and begins vomiting repeatedly; the liver is enlarged, transaminases are high and ammonia is raised, with no jaundice. Which complication has developed?

A 23-year-old woman attends the skin OPD with painful grouped vesicles and shallow ulcers on the vulva, appearing for the first time, with tender inguinal nodes and fever. A smear is taken from the base of a fresh vesicle and stained. Which finding supports the clinical diagnosis?

A 50-year-old man is admitted to a district hospital with hydrophobia, excessive salivation and episodes of terror, three months after an untreated dog bite. He is conscious between episodes. The family asks for every possible treatment. What is the most appropriate management?

A 20-year-old man with dengue fever is on day 5 of illness. His haematocrit has risen from 39% to 48% and there is free fluid in the abdomen on ultrasound, while the serum albumin has fallen. What is the main mechanism of this fluid shift?

A stray dog that bit three children in a Nagpur colony is killed the same day and its carcass is sent to the veterinary laboratory. Which test on the animal's brain is the standard method to confirm rabies?

During a Nipah outbreak, a medical officer in a Kerala district hospital must admit a patient with fever and encephalitis whose throat swab has been sent for Nipah RT-PCR. Which infection control measure is most appropriate while the result is awaited?

A 45-year-old man in a Pune hospital has hydrophobia, aerophobia and agitation two months after a dog bite for which he took no treatment. The family wants laboratory confirmation. Which specimen and test is most appropriate while he is alive?