An unimmunised 4-year-old had measles 10 days ago. He is now admitted with high fever and respiratory distress; WBC 18,000/µL with 85% neutrophils and a lobar shadow on the chest film. The most likely cause of his deterioration is:

Subacute sclerosing panencephalitis

A laboratory technician who has never been vaccinated against hepatitis B pricks her finger on a needle used for a patient who is HBsAg and HBeAg positive. The correct immediate management is:

Hepatitis B immunoglobulin with the first vaccine dose

Await her HBsAg result before acting

The vaccine course alone, starting next week

Immunoglobulin alone, repeated after a month

A second dengue infection with a different serotype carries a higher risk of severe disease because the antibodies from the first infection:

Destroy the patient's platelets

Neutralise the new serotype slowly

Virology: medically important viral diseases

36 Kerala PSC Lab Technician Gr II practice questions on Virology: medically important viral diseases, 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
An unimmunised 4-year-old had measles 10 days ago. He is now admitted with high fever and respiratory distress; WBC 18,000/µL with 85% neutrophils and a lobar shadow on the chest film. The most likely cause of his deterioration is:
1. ASecondary bacterial pneumonia
2. BSubacute sclerosing panencephalitis
3. CMeasles giant cell pneumonia
4. DAcute viral myocarditis
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Answer: A · Secondary bacterial pneumonia
Measles suppresses cell-mediated immunity for weeks and strips the respiratory epithelium, so bacterial pneumonia is the commonest complication and the leading cause of death. Measles itself causes a leucopenia, so a neutrophil count of 85% with a lobar shadow points to a secondary infection, usually Streptococcus pneumoniae or Staphylococcus aureus. Sputum or blood culture is sent, and the child is treated with antibiotics and vitamin A. Giant cell pneumonia is a measles pneumonia of immunodeficient children, without this neutrophil response.
- B: Subacute sclerosing panencephalitis is a late neurological complication appearing years afterwards.
- C: Giant cell pneumonia occurs in immunodeficient children and gives no neutrophil leucocytosis.
- D: Myocarditis is rare in measles and would not explain the lobar shadow.
Question 2 · Hard
A laboratory technician who has never been vaccinated against hepatitis B pricks her finger on a needle used for a patient who is HBsAg and HBeAg positive. The correct immediate management is:
1. AAwait her HBsAg result before acting
2. BThe vaccine course alone, starting next week
3. CHepatitis B immunoglobulin with the first vaccine dose
4. DImmunoglobulin alone, repeated after a month
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Answer: C · Hepatitis B immunoglobulin with the first vaccine dose
An HBeAg-positive source carries a high viral load, so the exposed person needs passive and active protection together, ideally within 24 hours. Hepatitis B immunoglobulin gives antibody at once, and the vaccine, started at the same time in the other arm, gives lasting protection. Waiting for her own markers or delaying the vaccine wastes the short window in which prophylaxis works. Baseline markers are still drawn, and follow-up testing is done at 3 and 6 months.
- A: Prophylaxis must not wait for her own test results.
- B: Vaccine alone, and delayed, leaves her unprotected during the critical first days.
- D: Immunoglobulin alone gives only temporary protection and no lasting immunity.
Question 3 · Easy
How does hepatitis A virus spread mainly?
1. AThe faecal-oral route
2. BSexual contact
3. CMosquito bites
4. DBlood transfusion
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Answer: A · The faecal-oral route
Hepatitis A is shed in the faeces late in the incubation period and spreads through contaminated water, food and hands, so outbreaks follow sewage contamination of a water supply. Hepatitis E spreads the same way; hepatitis B, C and D are blood-borne. Children often have mild or silent infection, while adults are more likely to become jaundiced. Infection leaves lifelong immunity, and a vaccine is available.
- B: Sexual spread is important for hepatitis B, not hepatitis A.
- C: No hepatitis virus is spread by mosquitoes.
- D: Blood-borne spread is the route of hepatitis B and C.
Question 4 · Medium
A second dengue infection with a different serotype carries a higher risk of severe disease because the antibodies from the first infection:
1. ADestroy the patient's platelets
2. BHelp the new virus enter cells
3. CBlock the antibody response
4. DNeutralise the new serotype slowly
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Answer: B · Help the new virus enter cells
Antibodies raised against one serotype bind the next serotype without neutralising it, and the antibody-coated virus is taken up through Fc receptors on monocytes and macrophages. This antibody-dependent enhancement raises the viral load and the cytokine response, leading to plasma leakage, a rising haematocrit and shock. It is one reason why dengue vaccines have been difficult to develop. The laboratory warning signs are a falling platelet count with a rising haematocrit.
- A: Thrombocytopenia follows the immune and cytokine response, not direct antibody attack on platelets.
- C: The antibody response to the second infection is brisk, not blocked.
- D: The problem is enhanced entry, not slow neutralisation.
Question 5 · Easy
After a dog bite, rabies virus reaches the central nervous system by travelling along:
1. ALymphatic vessels
2. BThe bloodstream
3. CCerebrospinal fluid
4. DPeripheral nerves
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Answer: D · Peripheral nerves
Rabies virus multiplies in muscle near the bite and then enters nerve endings, moving up the axons to the spinal cord and brain. It does not circulate in blood, which is why blood tests are of no help in diagnosis and why the incubation period depends on how far the bite is from the brain. Bites on the face and hands therefore carry the shortest incubation period. Wound washing and immunoglobulin at the site act before the virus enters the nerves.
- A: The virus is not carried in lymph.
- B: There is no viraemia in rabies, so blood tests do not help.
- C: Spread through the spinal fluid is not the route taken.
Question 6 · Easy
Which mosquito transmits dengue virus to humans?
1. AAedes aegypti
2. BMansonia species
3. CAnopheles stephensi
4. DCulex quinquefasciatus
Answer and explanation in LearnFree account
Question 7 · Medium
Influenza vaccine has to be reformulated almost every year because the virus shows:
1. AResistance to neuraminidase drugs
2. BA change from RNA to DNA
3. CAntigenic drift in its surface antigens
4. DLoss of its envelope in winter
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Question 8 · Medium
Compared with the injectable polio vaccine, the oral vaccine has the advantage that it:
1. AContains killed virus only
2. BCannot be given along with other vaccines
3. CProduces intestinal immunity as well
4. DNeeds no cold chain in the field
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Question 9 · Medium
What causes antigenic shift in influenza A, the change that can start a pandemic?
1. AReassortment of genome segments
2. BIntegration into host DNA
3. CLoss of the viral envelope
4. DPoint mutations in the HA gene
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Question 10 · Medium
To which molecule on helper T cells does the gp120 of HIV bind?
1. ACD19
2. BMHC class I
3. CCD4
4. DCD8
Answer and explanation in LearnFree account
Question 11 · Easy
An unvaccinated 3-year-old has fever, cough, red eyes and small bluish-white spots on the buccal mucosa opposite the molars. The most likely diagnosis is:
1. AMeasles
2. BChickenpox
3. CMumps
4. DRubella
Answer and explanation in LearnFree account
Question 12 · Medium
A 68-year-old woman has painful vesicles in a band over one side of her chest. The virus responsible had been lying dormant in her:
1. ASalivary glands
2. BSensory nerve ganglia
3. CB lymphocytes
4. DLiver cells
Answer and explanation in LearnFree account
Question 13 · Medium
Poliomyelitis causes flaccid paralysis without loss of sensation because the virus destroys:
1. AMyelin of peripheral nerves
2. BDorsal root ganglion cells
3. CAnterior horn cells of the spinal cord
4. DMuscle fibres of the limbs
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Question 14 · Easy
Which vector transmits Kyasanur Forest disease to humans?
1. APhlebotomus sandflies
2. BAedes mosquitoes
3. CCulex mosquitoes
4. DHaemaphysalis ticks
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Question 15 · Hard
A 24-year-old with dengue is on day 5 of fever. The fever has settled, but he has abdominal pain and persistent vomiting. Haematocrit has risen from 40% to 50% in 24 hours and platelets have fallen from 110,000 to 30,000/µL. What do these findings indicate?
1. AHaemorrhage from the low platelet count
2. BSimple dehydration from vomiting alone
3. CPlasma leakage, a warning sign of severe dengue
4. DRecovery, as the fever has settled
Answer and explanation in LearnFree account
Question 16 · Easy
Which animal is the natural reservoir of Nipah virus?
1. AFruit bat (Pteropus)
2. BDomestic dog
3. CDomestic pig
4. DHouse rat
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Question 17 · Hard
A newborn has bilateral cataracts, a patent ductus arteriosus and fails the hearing screen. His mother recalls a mild fever with a rash in the third month of pregnancy. The most likely congenital infection is:
1. AVaricella
2. BRubella
3. CHerpes simplex
4. DCytomegalovirus
Answer and explanation in LearnFree account
Question 18 · Easy
Which enzyme does HIV use to copy its RNA genome into DNA?
1. ANeuraminidase
2. BRNA-dependent RNA polymerase
3. CDNA gyrase
4. DReverse transcriptase
Answer and explanation in LearnFree account
Question 19 · Hard
A 9-year-old boy is bitten on the hand by a stray dog. The bite has broken the skin and is bleeding. He has never received rabies vaccine. Besides washing the wound well with soap and water, he needs:
1. ARabies vaccine alone, with no immunoglobulin
2. BObservation of the dog for 10 days before acting
3. CRabies immunoglobulin alone, with no vaccine
4. DRabies immunoglobulin into the wound and vaccine
Answer and explanation in LearnFree account
Question 20 · Medium
In the Nipah outbreaks in Kerala, cases among patients' relatives and nurses showed that the virus also spreads:
1. AFrom person to person through close contact
2. BThrough the bite of infected dogs
3. CThrough Culex mosquito bites
4. DThrough the faecal contamination of water
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Question 21 · Easy
Hepatitis D virus can cause infection only in a person who also has which infection?
1. AHepatitis E infection
2. BHepatitis C infection
3. CHepatitis A infection
4. DHepatitis B infection
Answer and explanation in LearnFree account
Question 22 · Medium
Compared with infection in adults, hepatitis B acquired at birth from a carrier mother:
1. AUsually causes fulminant hepatitis
2. BUsually becomes chronic, in about 90%
3. CCauses no lasting liver disease
4. DIs usually cleared within 6 months
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Question 23 · Medium
By the CDC definition, an adult with HIV infection has AIDS once the CD4 T-cell count falls below:
1. A500 cells/µL
2. B200 cells/µL
3. C350 cells/µL
4. D50 cells/µL
Answer and explanation in LearnFree account
Question 24 · Easy
Infection with which hepatitis virus most often becomes chronic in adults?
1. AHepatitis B virus
2. BHepatitis E virus
3. CHepatitis C virus
4. DHepatitis A virus
Answer and explanation in LearnFree account
Question 25 · Easy
A 17-year-old has fever, sore throat, enlarged neck nodes and a palpable spleen; the smear shows many reactive lymphocytes. Which virus is the usual cause?
1. AEpstein-Barr virus
2. BAdenovirus
3. CHuman herpesvirus 6
4. DCytomegalovirus
Answer and explanation in LearnFree account

11 more Virology: medically important viral diseases questions

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Virology: medically important viral diseases

An unimmunised 4-year-old had measles 10 days ago. He is now admitted with high fever and respiratory distress; WBC 18,000/µL with 85% neutrophils and a lobar shadow on the chest film. The most likely cause of his deterioration is:

A laboratory technician who has never been vaccinated against hepatitis B pricks her finger on a needle used for a patient who is HBsAg and HBeAg positive. The correct immediate management is:

How does hepatitis A virus spread mainly?

A second dengue infection with a different serotype carries a higher risk of severe disease because the antibodies from the first infection:

After a dog bite, rabies virus reaches the central nervous system by travelling along:

Which mosquito transmits dengue virus to humans?

Influenza vaccine has to be reformulated almost every year because the virus shows:

Compared with the injectable polio vaccine, the oral vaccine has the advantage that it:

What causes antigenic shift in influenza A, the change that can start a pandemic?

To which molecule on helper T cells does the gp120 of HIV bind?

An unvaccinated 3-year-old has fever, cough, red eyes and small bluish-white spots on the buccal mucosa opposite the molars. The most likely diagnosis is:

A 68-year-old woman has painful vesicles in a band over one side of her chest. The virus responsible had been lying dormant in her:

Poliomyelitis causes flaccid paralysis without loss of sensation because the virus destroys:

Which vector transmits Kyasanur Forest disease to humans?

A 24-year-old with dengue is on day 5 of fever. The fever has settled, but he has abdominal pain and persistent vomiting. Haematocrit has risen from 40% to 50% in 24 hours and platelets have fallen from 110,000 to 30,000/µL. What do these findings indicate?

Which animal is the natural reservoir of Nipah virus?

A newborn has bilateral cataracts, a patent ductus arteriosus and fails the hearing screen. His mother recalls a mild fever with a rash in the third month of pregnancy. The most likely congenital infection is:

Which enzyme does HIV use to copy its RNA genome into DNA?

A 9-year-old boy is bitten on the hand by a stray dog. The bite has broken the skin and is bleeding. He has never received rabies vaccine. Besides washing the wound well with soap and water, he needs:

In the Nipah outbreaks in Kerala, cases among patients' relatives and nurses showed that the virus also spreads:

Hepatitis D virus can cause infection only in a person who also has which infection?

Compared with infection in adults, hepatitis B acquired at birth from a carrier mother:

By the CDC definition, an adult with HIV infection has AIDS once the CD4 T-cell count falls below:

Infection with which hepatitis virus most often becomes chronic in adults?

A 17-year-old has fever, sore throat, enlarged neck nodes and a palpable spleen; the smear shows many reactive lymphocytes. Which virus is the usual cause?