What is the Dane particle seen in the serum of a person with hepatitis B?

A naked core particle without envelope

A filament of excess surface antigen

A sphere of excess surface antigen

Compared with street rabies virus, the fixed virus used for making vaccines has:

A short, fixed incubation and no Negri bodies

Growth mainly in the salivary glands of rabid dogs

Greater spread from bite sites to the brain

A long, variable incubation and Negri bodies

Virology

61 Kerala MSc MLT Entrance practice questions on Virology, 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 man with HIV has a WBC count of 4,500/µL, lymphocytes 20% of white cells, and CD4 T cells 15% of lymphocytes by flow cytometry. What is his absolute CD4 count?
1. A675 cells/µL
2. B1,350 cells/µL
3. C900 cells/µL
4. D135 cells/µL
Show answerHide answer
Answer: D · 135 cells/µL
Absolute lymphocytes = 4,500 × 0.20 = 900/µL. Absolute CD4 count = 900 × 0.15 = 135 cells/µL. Taking 15% of the total WBC gives 675, stopping at the lymphocyte count gives 900, and a decimal slip gives 1,350. A count below 200 cells/µL marks advanced HIV disease and a high risk of opportunistic infections such as Pneumocystis pneumonia.
- A: 675 takes 15% of the total WBC instead of the lymphocytes.
- B: 1,350 is a decimal slip, ten times the correct value.
- C: 900 is the absolute lymphocyte count, not the CD4 count.
Question 2 · Medium
What is the Dane particle seen in the serum of a person with hepatitis B?
1. AA naked core particle without envelope
2. BThe complete infectious virion
3. CA filament of excess surface antigen
4. DA sphere of excess surface antigen
Show answerHide answer
Answer: B · The complete infectious virion
Three kinds of particle are seen by electron microscopy in HBV-infected serum. The Dane particle, about 42 nm across, is the complete virion: a core of HBcAg with the DNA genome and polymerase, inside an envelope carrying HBsAg. The far more numerous 22 nm spheres and filaments are made of excess HBsAg only and are not infectious. Free core particles are not found in serum, which is why HBcAg is not measured in blood.
- A: Naked cores are not found free in serum; HBcAg is detected in liver cells.
- C: The filaments are also excess HBsAg without nucleic acid.
- D: The 22 nm spheres are excess HBsAg without nucleic acid and are not infectious.
Question 3 · Medium
Compared with street rabies virus, the fixed virus used for making vaccines has:
1. AGrowth mainly in the salivary glands of rabid dogs
2. BA short, fixed incubation and no Negri bodies
3. CGreater spread from bite sites to the brain
4. DA long, variable incubation and Negri bodies
Show answerHide answer
Answer: B · A short, fixed incubation and no Negri bodies
Pasteur adapted street virus by serial passage in rabbit brain until it became fixed. Fixed virus has a short, constant incubation period of about 4-6 days after intracerebral inoculation, rarely forms Negri bodies, and does not spread well from peripheral sites to the brain or to the salivary glands. These properties made it safe as a vaccine strain. Street virus, from naturally infected animals, has a long, variable incubation and forms Negri bodies.
- A: Salivary gland infection is a feature of street virus in rabid animals.
- C: Fixed virus has lost much of its ability to spread from peripheral sites to the brain.
- D: A long, variable incubation and Negri bodies are features of street virus.
Question 4 · Hard
In May, a 14-year-old boy in Kozhikode district develops fever, vomiting, confusion and breathing difficulty. His father died of a similar illness a week ago, and a nurse who cared for the father is now febrile. Fruit bats roost in an orchard beside the house. CSF: 60 cells/µL, mostly lymphocytes, with mildly raised protein. The most likely cause is:
1. ANipah virus
2. BRabies virus
3. CKyasanur Forest disease virus
4. DJapanese encephalitis virus
Show answerHide answer
Answer: A · Nipah virus
Acute encephalitis with respiratory involvement, a cluster in a family and a health worker, and fruit bats nearby point to Nipah virus, a henipavirus of the family Paramyxoviridae that has caused several outbreaks in Kozhikode and nearby districts since 2018. Pteropus fruit bats are the reservoir, and the virus spreads from person to person through respiratory secretions and close contact. Throat swab, urine, blood and CSF are tested by RT-PCR in a high-containment laboratory under strict biosafety. Japanese encephalitis and Kyasanur Forest disease are vector-borne with no person-to-person spread, and rabies needs an animal bite.
- B: Rabies follows an animal bite and does not spread from a patient to caregivers in this way.
- C: KFD is tick-borne, causes a haemorrhagic fever and does not spread from person to person.
- D: JE is mosquito-borne and humans are dead-end hosts, so it does not spread to family members and nurses.
Question 5 · Easy
Large cells with an 'owl's-eye' intranuclear inclusion in a tissue section suggest infection with:
1. AMeasles virus
2. BCytomegalovirus
3. CPoxvirus
4. DRabies virus
Show answerHide answer
Answer: B · Cytomegalovirus
Cytomegalovirus makes infected cells swell (cytomegaly) and forms a large, dense intranuclear inclusion separated from the nuclear membrane by a clear halo, giving an owl's-eye look. Smaller cytoplasmic inclusions may also be present. These cells are seen in tissues, urine sediment and placenta in congenital and transplant-related CMV disease. Rabies forms cytoplasmic Negri bodies, measles forms multinucleate giant cells, and poxviruses form cytoplasmic Guarnieri bodies.
- A: Measles virus forms multinucleate giant cells with inclusions, not owl's-eye cells.
- C: Poxviruses form cytoplasmic Guarnieri bodies.
- D: Rabies virus forms cytoplasmic Negri bodies, not intranuclear inclusions.
Question 6 · Easy
Which of the hepatitis viruses has a DNA genome?
1. AHepatitis E virus
2. BHepatitis C virus
3. CHepatitis A virus
4. DHepatitis B virus
Answer and explanation in LearnFree account
Question 7 · Medium
During an outbreak of jaundice in a Kerala town traced to a contaminated drinking-water supply, adult patients test IgM anti-HAV negative and HBsAg negative. Which test should be done next?
1. AIgG anti-HAV
2. BIgM anti-HBc
3. CAnti-HCV antibody
4. DIgM anti-HEV
Answer and explanation in LearnFree account
Question 8 · Hard
Paired sera are tested by haemagglutination inhibition without pretreatment. Both acute and convalescent sera inhibit at 1:640 against influenza A(H1N1), A(H3N2) and B antigens alike, and the serum controls (no antigen) show no agglutination. What is the most likely problem?
1. AToo much antigen used, above 4 HA units
2. BPast infection with all three influenza viruses
3. CNatural agglutinins against the red cells
4. DNonspecific inhibitors not removed by RDE treatment
Answer and explanation in LearnFree account
Question 9 · Easy
What kind of genome does rotavirus, the leading cause of severe diarrhoea in infants, have?
1. ASingle-stranded linear DNA
2. BDouble-stranded circular DNA
3. CSegmented double-stranded RNA
4. DSingle-stranded positive-sense RNA
Answer and explanation in LearnFree account
Question 10 · Hard
A 45-year-old woman in Thrissur has had fever for 3 days with a maculopapular rash and severe, symmetrical pain and swelling of the small joints of her hands and wrists. Platelets are 2.1 lakh/µL and dengue NS1 is negative. Which test is most likely to confirm the diagnosis now?
1. AChikungunya IgM ELISA on serum
2. BRepeat dengue NS1 after 5 days
3. CDengue IgG ELISA on serum
4. DChikungunya RT-PCR on serum
Answer and explanation in LearnFree account
Question 11 · Medium
Rubella virus produces no visible CPE in African green monkey kidney cells. It is still detected in these cells because the infected cells:
1. AFuse into syncytia visible after staining
2. BRelease a toxin that lyses fresh cells
3. CResist the CPE of a challenge enterovirus
4. DShow cytoplasmic Negri-like inclusions
Answer and explanation in LearnFree account
Question 12 · Medium
What are Negri bodies, the structures sought in brain tissue in rabies?
1. AEosinophilic inclusions in the neuron cytoplasm
2. BEosinophilic inclusions in the neuron nucleus
3. CClusters of activated microglia around the neurons
4. DBasophilic inclusions in the neuron nucleus
Answer and explanation in LearnFree account
Question 13 · Hard
In a dengue real-time RT-PCR run, the positive control has Ct 26 and the no-template control has Ct 34. Three patient samples have Ct values of 31, 33 and 35. What should the laboratory do?
1. ASubtract the control Ct and report the remainder
2. BReport all three patients as dengue positive
3. CReport only the patient with Ct 31 as positive
4. DReject the run, decontaminate and repeat with fresh reagents
Answer and explanation in LearnFree account
Question 14 · Medium
Most rapid antigen tests for COVID-19 on a nasal swab detect which SARS-CoV-2 component?
1. AThe viral RNA genome
2. BThe nucleocapsid protein
3. CThe spike protein receptor-binding domain
4. DHost IgM made against the virus
Answer and explanation in LearnFree account
Question 15 · Easy
Under the electron microscope, rabies virus has a characteristic shape described as:
1. ABrick-shaped
2. BWheel-shaped
3. CBullet-shaped
4. DFilamentous and branched
Answer and explanation in LearnFree account
Question 16 · Hard
A 2-year-old at a day-care centre has low fever, painful ulcers on the tongue and palate, and small grey vesicles on the palms, soles and buttocks. Several other children have similar lesions. The most likely cause is:
1. AVaricella-zoster virus
2. BCoxsackievirus A16
3. CHerpes simplex virus 1
4. DMeasles virus
Answer and explanation in LearnFree account
Question 17 · Easy
How many separate RNA segments make up the genome of influenza A virus?
1. AEight
2. BSeven
3. CTen
4. DEleven
Answer and explanation in LearnFree account
Question 18 · Medium
A child with sickle cell anaemia suddenly has a haemoglobin of 4 g/dL with a reticulocyte count near 0%. Parvovirus B19 is suspected because the virus:
1. AInfects erythroid precursors via the P antigen
2. BLyses mature red cells in the circulation
3. CCauses autoimmune haemolysis by cold agglutinins
4. DInfects megakaryocytes and stops platelet release
Answer and explanation in LearnFree account
Question 19 · Medium
People homozygous for the CCR5 delta-32 deletion are highly resistant to infection with most HIV-1 strains. This is because:
1. ACCR5 is the main receptor for HIV gp41
2. BThe deletion removes CD4 from helper T cells
3. CMost transmitted strains need CCR5 as a co-receptor
4. DCCR5 is needed for reverse transcription
Answer and explanation in LearnFree account
Question 20 · Medium
In the electron microscopic examination of stool for viruses such as rotavirus, the particles are made visible by negative staining with:
1. ALugol's iodine
2. BCrystal violet
3. CPhosphotungstic acid
4. DOsmium tetroxide
Answer and explanation in LearnFree account
Question 21 · Easy
In a young adult man, the most common complication of mumps is:
1. ADeafness
2. BEncephalitis
3. CPancreatitis
4. DOrchitis
Answer and explanation in LearnFree account
Question 22 · Medium
The Semple rabies vaccine was withdrawn in India and replaced by cell culture vaccines mainly because it:
1. ACaused neuroparalytic reactions from sheep brain tissue
2. BNeeded only one dose and gave short protection
3. CCould not be stored without liquid nitrogen
4. DContained live street virus that caused rabies
Answer and explanation in LearnFree account
Question 23 · Medium
Which tumour, relatively common in parts of north-east India and southern China, is strongly associated with Epstein-Barr virus?
1. ACarcinoma of the cervix
2. BNasopharyngeal carcinoma
3. CHepatocellular carcinoma
4. DAdult T-cell leukaemia
Answer and explanation in LearnFree account
Question 24 · Hard
An HIV ELISA has a sensitivity of 100% and a specificity of 99.8%. It is used on 10,000 donors in whom the true prevalence of HIV is 0.2%. About what proportion of the reactive results will be true positives?
1. AAbout 100%
2. BAbout 99.8%
3. CAbout 50%
4. DAbout 0.2%
Answer and explanation in LearnFree account
Question 25 · Medium
Rhinoviruses and enteroviruses are both picornaviruses. Which property best separates rhinoviruses from enteroviruses in the laboratory?
1. ARhinoviruses have a DNA genome
2. BRhinoviruses carry a lipid envelope
3. CRhinoviruses are destroyed at pH 3
4. DRhinoviruses grow best at 37 °C
Answer and explanation in LearnFree account

36 more Virology questions

Answer them one by one, keep your score and see your weak topics in Learn. Signed-out visitors try 25 per exam; sign in with Google to see them all.

Study Microbiology

Virology

A man with HIV has a WBC count of 4,500/µL, lymphocytes 20% of white cells, and CD4 T cells 15% of lymphocytes by flow cytometry. What is his absolute CD4 count?

What is the Dane particle seen in the serum of a person with hepatitis B?

Compared with street rabies virus, the fixed virus used for making vaccines has:

Large cells with an 'owl's-eye' intranuclear inclusion in a tissue section suggest infection with:

Which of the hepatitis viruses has a DNA genome?

During an outbreak of jaundice in a Kerala town traced to a contaminated drinking-water supply, adult patients test IgM anti-HAV negative and HBsAg negative. Which test should be done next?

Paired sera are tested by haemagglutination inhibition without pretreatment. Both acute and convalescent sera inhibit at 1:640 against influenza A(H1N1), A(H3N2) and B antigens alike, and the serum controls (no antigen) show no agglutination. What is the most likely problem?

What kind of genome does rotavirus, the leading cause of severe diarrhoea in infants, have?

A 45-year-old woman in Thrissur has had fever for 3 days with a maculopapular rash and severe, symmetrical pain and swelling of the small joints of her hands and wrists. Platelets are 2.1 lakh/µL and dengue NS1 is negative. Which test is most likely to confirm the diagnosis now?

Rubella virus produces no visible CPE in African green monkey kidney cells. It is still detected in these cells because the infected cells:

What are Negri bodies, the structures sought in brain tissue in rabies?

In a dengue real-time RT-PCR run, the positive control has Ct 26 and the no-template control has Ct 34. Three patient samples have Ct values of 31, 33 and 35. What should the laboratory do?

Most rapid antigen tests for COVID-19 on a nasal swab detect which SARS-CoV-2 component?

Under the electron microscope, rabies virus has a characteristic shape described as:

A 2-year-old at a day-care centre has low fever, painful ulcers on the tongue and palate, and small grey vesicles on the palms, soles and buttocks. Several other children have similar lesions. The most likely cause is:

How many separate RNA segments make up the genome of influenza A virus?

A child with sickle cell anaemia suddenly has a haemoglobin of 4 g/dL with a reticulocyte count near 0%. Parvovirus B19 is suspected because the virus:

People homozygous for the CCR5 delta-32 deletion are highly resistant to infection with most HIV-1 strains. This is because:

In the electron microscopic examination of stool for viruses such as rotavirus, the particles are made visible by negative staining with:

In a young adult man, the most common complication of mumps is:

The Semple rabies vaccine was withdrawn in India and replaced by cell culture vaccines mainly because it:

Which tumour, relatively common in parts of north-east India and southern China, is strongly associated with Epstein-Barr virus?

An HIV ELISA has a sensitivity of 100% and a specificity of 99.8%. It is used on 10,000 donors in whom the true prevalence of HIV is 0.2%. About what proportion of the reactive results will be true positives?

Rhinoviruses and enteroviruses are both picornaviruses. Which property best separates rhinoviruses from enteroviruses in the laboratory?