Educational information only — not a diagnosis. Always talk to a qualified doctor.
LabologicsUnderstand your labs اردو

Exam Prep

Virology practice questions.

Lab methods, hepatitis viruses, herpesviruses, respiratory viruses, childhood exanthems and other important viruses.

All subjects

Independent practice questions written by Labologics. Not affiliated with DHA, DOH (formerly HAAD), SCFHS, Prometric or any exam body. Not recalled exam questions.

Basics & methods

Q1 Basics & methods · Easy

Viruses are grown in the laboratory using:

  1. A: Cell (tissue) culture, looking for cytopathic effect
  2. B: MacConkey agar
  3. C: Sabouraud agar
  4. D: Blood agar
Show answer

Answer: A — Cell (tissue) culture, looking for cytopathic effect

Viruses replicate only inside living cells. Today, molecular tests (PCR) and antigen tests have largely replaced routine culture.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q2 Basics & methods · Medium

How should most specimens for viral testing be transported?

  1. A: Dry swab at room temperature for 3 days
  2. B: In viral transport medium, refrigerated at 2-8 C
  3. C: In formalin
  4. D: In blood culture bottles
Show answer

Answer: B — In viral transport medium, refrigerated at 2-8 C

If a delay of more than about 48-72 hours is expected, freeze at -70 C; avoid -20 C freezers.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q3 Basics & methods · Medium

Which is a non-enveloped virus that resists alcohol hand rubs and spreads in outbreaks?

  1. A: Herpes simplex virus
  2. B: Influenza virus
  3. C: Norovirus
  4. D: HIV
Show answer

Answer: C — Norovirus

Enveloped viruses (influenza, HIV, herpes, coronaviruses) are easily inactivated by detergents and alcohol; norovirus outbreaks need soap and water and hypochlorite.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q4 Basics & methods · Hard

Most DNA viruses replicate in the nucleus. Which DNA virus family replicates in the cytoplasm?

  1. A: Adenoviruses
  2. B: Papillomaviruses
  3. C: Herpesviruses
  4. D: Poxviruses
Show answer

Answer: D — Poxviruses

Poxviruses carry their own enzymes for cytoplasmic replication.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q5 Basics & methods · Medium

Routine diagnostic PCR testing on SARS-CoV-2 specimens is generally done at:

  1. A: BSL-2 with BSL-3 practices for aerosol-generating steps; virus culture requires BSL-3
  2. B: BSL-4 only
  3. C: No containment
  4. D: BSL-1
Show answer

Answer: A — BSL-2 with BSL-3 practices for aerosol-generating steps; virus culture requires BSL-3

Follow national and WHO biosafety guidance for respiratory virus testing.

Reference: CDC clinical and laboratory guidance (viral diseases)

Hepatitis viruses

Q6 Hepatitis viruses · Easy

Which hepatitis viruses are spread by the fecal-oral route through contaminated food and water?

  1. A: Hepatitis B and C
  2. B: Hepatitis A and E
  3. C: Hepatitis D only
  4. D: Hepatitis B and D
Show answer

Answer: B — Hepatitis A and E

Acute hepatitis A is diagnosed with IgM anti-HAV. Hepatitis E can be severe in pregnancy and is common in South Asia.

Reference: CDC clinical and laboratory guidance (viral diseases)

Q7 Hepatitis viruses · Easy

The first marker to appear after hepatitis B infection is:

  1. A: Anti-HBc IgG
  2. B: Anti-HBs
  3. C: HBsAg
  4. D: Anti-HBe
Show answer

Answer: C — HBsAg

Acute infection is shown by HBsAg with IgM anti-HBc. Recovery is shown by anti-HBs with anti-HBc.

Reference: CDC: Interpretation of Hepatitis B Serologic Test Results

Q8 Hepatitis viruses · Medium

Which marker best indicates high infectivity in hepatitis B?

  1. A: Anti-HBc IgG
  2. B: Anti-HBe
  3. C: Anti-HBs
  4. D: HBeAg (and high HBV DNA)
Show answer

Answer: D — HBeAg (and high HBV DNA)

Mothers who are HBeAg positive have the highest risk of transmitting HBV to their babies.

Reference: CDC: Interpretation of Hepatitis B Serologic Test Results

Q9 Hepatitis viruses · Medium

A baby is born to an HBsAg-positive mother. The baby should receive:

  1. A: Hepatitis B vaccine and hepatitis B immune globulin (HBIG) within 12 hours of birth
  2. B: Antibiotics
  3. C: Only breastfeeding advice
  4. D: Nothing until 6 months
Show answer

Answer: A — Hepatitis B vaccine and hepatitis B immune globulin (HBIG) within 12 hours of birth

The vaccine series is completed and the infant is tested for HBsAg and anti-HBs at 9-12 months.

Reference: CDC clinical and laboratory guidance (viral diseases)

Q10 Hepatitis viruses · Hard

HBV viral load is measured by:

  1. A: RT-PCR for HBV RNA
  2. B: Real-time PCR for HBV DNA
  3. C: HBsAg ELISA
  4. D: Anti-HBc IgM
Show answer

Answer: B — Real-time PCR for HBV DNA

HBV is a DNA virus. RT-PCR is used for RNA viruses such as HCV and HIV.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q11 Hepatitis viruses · Medium

Hepatitis D (delta) infection in a person who already has chronic hepatitis B is called:

  1. A: Seroconversion
  2. B: Coinfection
  3. C: Superinfection
  4. D: Reactivation
Show answer

Answer: C — Superinfection

HDV needs HBsAg to replicate. Simultaneous acute HBV and HDV infection is coinfection; superinfection more often becomes chronic and severe.

Reference: CDC clinical and laboratory guidance (viral diseases)

Q12 Hepatitis viruses · Medium

After 6 months of treatment for hepatitis C, which test checks whether the virus is still present?

  1. A: HBsAg
  2. B: ALT alone
  3. C: Anti-HCV antibody
  4. D: Quantitative HCV RNA (viral load)
Show answer

Answer: D — Quantitative HCV RNA (viral load)

Anti-HCV usually stays positive for life even after cure. Sustained undetectable HCV RNA after treatment means cure.

Reference: CDC clinical and laboratory guidance (viral diseases)

Q13 Hepatitis viruses · Easy

Which hepatitis virus has historically been the most common cause of post-transfusion hepatitis?

  1. A: Hepatitis C
  2. B: Hepatitis E
  3. C: Hepatitis D
  4. D: Hepatitis A
Show answer

Answer: A — Hepatitis C

Donor screening with anti-HCV and NAT has made this rare. Today, bacterial contamination (especially of platelets) is the most common infectious transfusion risk.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Herpesviruses

Q14 Herpesviruses · Easy

Infectious mononucleosis (fever, sore throat, lymphadenopathy, splenomegaly) is usually caused by:

  1. A: Cytomegalovirus
  2. B: Epstein-Barr virus
  3. C: Herpes simplex virus
  4. D: Adenovirus
Show answer

Answer: B — Epstein-Barr virus

EBV spreads through saliva. Blood shows reactive lymphocytes; heterophile antibodies (monospot) are positive.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q15 Herpesviruses · Medium

Which EBV antibody pattern indicates acute (recent) infection?

  1. A: EBNA IgG only
  2. B: VCA IgG only, EBNA positive
  3. C: VCA IgM positive, EBNA negative
  4. D: All antibodies negative
Show answer

Answer: C — VCA IgM positive, EBNA negative

Antibody to EBNA appears weeks to months later, so its presence suggests past infection. There is no licensed EBV vaccine.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q16 Herpesviruses · Medium

EBV is associated with which cancers?

  1. A: Cervical cancer
  2. B: Hepatocellular carcinoma only
  3. C: Kaposi sarcoma only
  4. D: Burkitt lymphoma and nasopharyngeal carcinoma
Show answer

Answer: D — Burkitt lymphoma and nasopharyngeal carcinoma

Kaposi sarcoma is caused by HHV-8; cervical cancer by HPV.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q17 Herpesviruses · Medium

Large cells with 'owl's eye' intranuclear inclusions in a biopsy indicate:

  1. A: Cytomegalovirus
  2. B: Rabies
  3. C: HPV
  4. D: Measles
Show answer

Answer: A — Cytomegalovirus

CMV causes congenital infection and disease in transplant and HIV patients. CMV-safe (seronegative or leukoreduced) blood is used for at-risk patients.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q18 Herpesviruses · Medium

Which test is preferred today to diagnose herpes simplex from a vesicle swab or CSF?

  1. A: Tzanck smear
  2. B: HSV PCR
  3. C: Heterophile test
  4. D: Culture on blood agar
Show answer

Answer: B — HSV PCR

The Tzanck smear (multinucleated giant cells) cannot tell HSV from VZV and is insensitive. HSV-1 mainly causes oral lesions and HSV-2 mainly genital lesions, but both can infect either site.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q19 Herpesviruses · Medium

A pregnant woman is exposed to chickenpox. Which test shows whether she is already protected?

  1. A: Rapid strep test
  2. B: VZV PCR of blood
  3. C: VZV IgG antibody
  4. D: Tzanck smear
Show answer

Answer: C — VZV IgG antibody

If she is VZV IgG negative, varicella-zoster immune globulin can be given. PCR of a vesicle is used to diagnose active infection.

Reference: CDC clinical and laboratory guidance (viral diseases)

Q20 Herpesviruses · Easy

Which virus family establishes lifelong latency with possible reactivation (e.g., shingles, cold sores)?

  1. A: Rotavirus
  2. B: Influenza virus
  3. C: Norovirus
  4. D: Herpesviruses
Show answer

Answer: D — Herpesviruses

VZV reactivates as shingles; HSV reactivates as recurrent cold sores or genital lesions.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Respiratory viruses

Q21 Respiratory viruses · Easy

The most common cause of bronchiolitis in infants is:

  1. A: Respiratory syncytial virus (RSV)
  2. B: Rotavirus
  3. C: Hepatitis A
  4. D: EBV
Show answer

Answer: A — Respiratory syncytial virus (RSV)

Diagnose with a molecular or antigen test on a nasopharyngeal specimen.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q22 Respiratory viruses · Easy

Croup (barking cough and stridor) in young children is most often caused by:

  1. A: Mumps
  2. B: Parainfluenza virus
  3. C: Rhinovirus
  4. D: HPV
Show answer

Answer: B — Parainfluenza virus

Parainfluenza type 1 is the classic cause.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q23 Respiratory viruses · Medium

Major changes in influenza A surface antigens (new H or N subtypes) that can cause pandemics are called:

  1. A: Reactivation
  2. B: Antigenic drift
  3. C: Antigenic shift
  4. D: Latency
Show answer

Answer: C — Antigenic shift

Drift is gradual point mutation, causing seasonal epidemics; shift is genetic reassortment.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q24 Respiratory viruses · Easy

The confirmatory test for SARS-CoV-2 or MERS-CoV is:

  1. A: Ferritin
  2. B: ESR
  3. C: D-dimer
  4. D: RT-PCR (NAAT) on a respiratory specimen
Show answer

Answer: D — RT-PCR (NAAT) on a respiratory specimen

D-dimer, ferritin and CRP help assess severity but are not diagnostic. MERS-CoV is linked to contact with dromedary camels.

Reference: CDC clinical and laboratory guidance (viral diseases)

Q25 Respiratory viruses · Medium

Pharyngitis with conjunctivitis after swimming in a pool suggests:

  1. A: Adenovirus
  2. B: Rotavirus
  3. C: Hepatitis E
  4. D: HTLV-1
Show answer

Answer: A — Adenovirus

Adenovirus is non-enveloped and resists chlorine. An eye swab or throat swab is used for PCR.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Exanthems & childhood viruses

Q26 Exanthems & childhood viruses · Easy

Tiny white spots on the inner cheek (Koplik spots) before a rash suggest:

  1. A: Chickenpox
  2. B: Measles
  3. C: Rubella
  4. D: Mumps
Show answer

Answer: B — Measles

Confirm with measles IgM or PCR. In Pakistan, measles vaccine is given at 9 and 15 months.

Reference: CDC clinical and laboratory guidance (viral diseases)

Q27 Exanthems & childhood viruses · Easy

Painful swelling of the parotid glands is characteristic of:

  1. A: Rubella virus
  2. B: Adenovirus
  3. C: Mumps virus
  4. D: Measles virus
Show answer

Answer: C — Mumps virus

Complications include orchitis, meningitis and pancreatitis.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q28 Exanthems & childhood viruses · Medium

Cataracts, deafness and a heart defect (e.g., PDA) in a newborn suggest:

  1. A: Congenital toxoplasmosis
  2. B: Neonatal herpes
  3. C: Rotavirus infection
  4. D: Congenital rubella syndrome
Show answer

Answer: D — Congenital rubella syndrome

Rubella-specific IgM in the newborn confirms congenital infection, because IgM does not cross the placenta.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q29 Exanthems & childhood viruses · Easy

The leading viral cause of severe watery diarrhea in infants and young children is:

  1. A: Rotavirus
  2. B: Hepatitis A
  3. C: Rubella
  4. D: HSV
Show answer

Answer: A — Rotavirus

Detect with stool antigen tests or PCR. A rotavirus vaccine is part of many national schedules, including Pakistan's.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q30 Exanthems & childhood viruses · Medium

Poliovirus is shed in and spread through:

  1. A: Respiratory droplets only
  2. B: Stool (fecal-oral route)
  3. C: Mosquito bites
  4. D: Blood transfusion only
Show answer

Answer: B — Stool (fecal-oral route)

Environmental (sewage) surveillance is important in countries such as Pakistan where wild poliovirus persists.

Reference: CDC clinical and laboratory guidance (viral diseases)

Other important viruses

Q31 Other important viruses · Medium

Which test is best in the first 5 days of a suspected dengue fever?

  1. A: Monospot
  2. B: Dengue IgG only
  3. C: Dengue NS1 antigen (or RT-PCR)
  4. D: Widal test
Show answer

Answer: C — Dengue NS1 antigen (or RT-PCR)

IgM becomes more useful after day 5. A positive tourniquet test and falling platelets support the diagnosis.

Reference: CDC clinical and laboratory guidance (viral diseases)

Q32 Other important viruses · Easy

Eosinophilic cytoplasmic inclusions (Negri bodies) in neurons are characteristic of:

  1. A: CMV
  2. B: Measles
  3. C: Herpes simplex
  4. D: Rabies virus
Show answer

Answer: D — Rabies virus

Rabies is mostly transmitted by dog bites in Pakistan and is almost always fatal once symptoms appear; post-exposure prophylaxis is urgent.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q33 Other important viruses · Medium

Which virus causes most cervical cancers?

  1. A: High-risk human papillomavirus (types 16, 18)
  2. B: EBV
  3. C: CMV
  4. D: Herpes simplex virus 2
Show answer

Answer: A — High-risk human papillomavirus (types 16, 18)

Koilocytes on Pap smear suggest HPV. HPV testing is used in cervical screening.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q34 Other important viruses · Medium

Adult T-cell leukemia/lymphoma is caused by:

  1. A: HIV-1
  2. B: HTLV-1
  3. C: EBV
  4. D: HHV-8
Show answer

Answer: B — HTLV-1

HTLV-1 also causes HTLV-associated myelopathy. Some countries screen blood donors for HTLV.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q35 Other important viruses · Medium

Which test detects HIV infection earliest after exposure?

  1. A: CD4 count
  2. B: Antibody-only rapid test
  3. C: HIV RNA (nucleic acid test)
  4. D: Western blot
Show answer

Answer: C — HIV RNA (nucleic acid test)

NAT detects infection before antibodies or p24 antigen. 4th generation antigen/antibody tests are used for screening.

Reference: CDC clinical and laboratory guidance (viral diseases)

Q36 Other important viruses · Easy

CSF with lymphocytes, normal glucose and mildly raised protein suggests:

  1. A: Fungal meningitis
  2. B: Subarachnoid hemorrhage
  3. C: Bacterial meningitis
  4. D: Viral meningitis
Show answer

Answer: D — Viral meningitis

Enteroviruses are the most common cause; PCR confirms the diagnosis.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q37 Other important viruses · Easy

The amount of virus in the bloodstream, measured by quantitative PCR, is called the:

  1. A: Viral load
  2. B: CD4 count
  3. C: Avidity
  4. D: Titer
Show answer

Answer: A — Viral load

Viral load monitors treatment of HIV, HBV, HCV and CMV.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology

Q38 Other important viruses · Medium

Mandatory infectious disease screening of donated blood in most countries includes:

  1. A: No testing
  2. B: HIV, hepatitis B, hepatitis C and syphilis (plus malaria in endemic areas)
  3. C: Influenza only
  4. D: EBV and CMV for all donors
Show answer

Answer: B — HIV, hepatitis B, hepatitis C and syphilis (plus malaria in endemic areas)

Some countries also test for HTLV-1/2 or use NAT.

Reference: Mahon & Lehman: Textbook of Diagnostic Microbiology