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Viral infections & hepatitis flashcards

16 high-yield MRCP Part 1 cards from the Intellect Medicos Infectious Diseases course. Try to answer each question before you open it — then study them properly with spaced repetition, which brings each card back just before you would forget it.

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1. Small gradual mutations in influenza surface antigens are called antigenic ______ (seasonal epidemics); sudden reassortment of a new subtype, seen only in influenza A, is antigenic shift (pandemics).

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   drift

   Why? Drift is why the vaccine is updated every year; shift produces a virus to which the population has no immunity.

2. Small gradual mutations in influenza surface antigens are called antigenic drift (seasonal epidemics); sudden reassortment of a new subtype, seen only in influenza A, is antigenic ______ (pandemics).

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   shift

   Why? Drift is why the vaccine is updated every year; shift produces a virus to which the population has no immunity.

3. What is the first-line antiviral for influenza in at-risk adults, and how does it work?

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   Oral oseltamivir — a neuraminidase inhibitor that stops new virus particles being released from infected cells.

   Why? Greatest benefit if started within 48 hours of onset, although UKHSA says later treatment is still worthwhile in at-risk or hospitalised patients. It can be used in pregnancy.

4. What is the first-line treatment for croup?

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   A single dose of oral dexamethasone (0.15 mg/kg).

   Why? Steroids reduce subglottic oedema. Nebulised adrenaline is added for moderate–severe croup.

5. A woman 16 weeks pregnant had close contact with a child with chickenpox 2 days ago. She cannot recall having chickenpox. What is the first step?

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   Urgently check her varicella-zoster IgG.

   Why? Most adults are immune even without a history. If IgG is positive, reassure.

6. A pregnant woman of 24 weeks develops a chickenpox rash. What should she be given?

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   Oral aciclovir, started within 24 hours of the rash appearing.

   Why? Varicella pneumonia is more severe in pregnancy; early antiviral treatment reduces complications.

7. Within what time window should antivirals ideally be started for shingles?

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   Within 72 hours of rash onset.

   Why? Early aciclovir/valaciclovir speeds healing and may reduce acute pain; post-herpetic neuralgia is the main complication.

8. What is the pathognomonic early sign of measles seen on the buccal mucosa?

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   Koplik spots (white/blue spots that appear before the rash).

   Why? Measles: cough, coryza, conjunctivitis, then a maculopapular rash that starts behind the ears and spreads downwards.

9. What is the commonest cause of death from measles?

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   Pneumonia.

   Why? Other complications include encephalitis, otitis media and, years later, subacute sclerosing panencephalitis (SSPE).

10. What post-exposure prophylaxis is offered to a measles contact who is pregnant or immunocompromised?

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    Normal immunoglobulin: IV immunoglobulin (IVIG) if immunosuppressed; intramuscular/subcutaneous HNIG for an immunocompetent pregnant woman.

    Why? MMR is live, so it cannot be given to these groups. Immunocompetent, non-pregnant, non-immune contacts can have MMR, ideally within 3 days (72 hours) of exposure.

11. What rash develops if a patient with infectious mononucleosis is given amoxicillin?

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    A widespread itchy maculopapular rash (common in this setting).

    Why? It is an EBV-related drug reaction rather than a true lasting penicillin allergy.

12. Parvovirus B19 infection in a patient with sickle cell disease can cause which acute haematological crisis?

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    Aplastic crisis (transient red cell aplasia with low reticulocytes).

    Why? Parvovirus B19 infects erythroid progenitors; in chronic haemolysis the red cell lifespan is short, so Hb falls sharply.

13. Name the classic triad of congenital rubella syndrome.

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    Sensorineural deafness, cataracts and congenital heart disease (especially patent ductus arteriosus).

    Why? Risk is highest when infection occurs in the first trimester.

14. What is the post-exposure management for a bite from a possibly rabid animal abroad in an unvaccinated person?

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    Thorough wound washing, then a course of rabies vaccine plus rabies immunoglobulin (for high-risk exposures).

    Why? Rabies is almost always fatal once symptoms start, so PEP must be prompt. Risk is assessed with UKHSA.

15. Which hepatitis B serology marker indicates ACUTE infection?

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    IgM anti-HBc (with HBsAg positive).

    Why? HBsAg means current infection (acute or chronic); IgM anti-HBc points to recent infection.

16. What is the treatment for chronic hepatitis C infection?

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    Oral direct-acting antivirals (DAAs), e.g. sofosbuvir-based combinations, for 8–12 weeks.

    Why? DAAs cure most patients (sustained virological response). Diagnosis: HCV antibody, then HCV RNA (PCR) to confirm active infection.