Viral Infections

Viral Infections

Childhood viral infections – see Paediatrics chapter.

Herpes simplex virus (HSV) infections:
two strains of HSV – type 1 (cold sores, keratoconjunctivitis, finger infections (whitlow), encephalitis, genital infections) and type 2 (sexually transmitted anogenital infections)

Poliomyelitis:
• see Neurology

Influenza:
• 3 different influenza viruses – A, B and C
• incubation period of 1-3 days – virus is shed for 3-7 days
• influenza A & B  sudden onset of fever, rigors, headache, malaise, joint aches, dry cough, nasal discharge
• influenza C  upper respiratory symptoms
• complication – pneumonia, secondary bacterial respiratory infection, exacerbation of asthma and bronchitis.
• Management – amantadine and rimantadine if given early

Viral Haemorrhagic fevers:
a) Lassa fever:
• due to the single stranded RNA virus adrenavirus in sub-Saharan West Africa. Reservoir is the multimammate rat
• small outbreaks are common – spread by person-to-person contact
• cause fever, intercostal Myalla, bradycardia, hypotension, leukopenia  can progress to renal and liver failure, haemorrhage and circulatory collapse
• treatment – isolation, tribavirin. 50% mortality

b) Yellow Fever:
• due to flavivirus from monkeys and transmitted by Aedes mosquitoes in tropical Africa, South and Central America; 2-14 day incubation
• mild febrile illness – starts suddenly with fever and rigours – can get severe backache, headache and bone pains

c) Marbug/Ebola virus disease:
• due to filovirus transmitted via monkey body fluid in Central Africa
• presents suddenly with fever, severe myalgias, and diarrhoea  progresses to lymphadenopathy, haemorrhage, encephalitis, renal failure and pneumonia

d) Dengue:
• due to flavivirus (dengue types 1-4) in tropical and subtropical coasts.
• prodrome of a few days of malaise and headache  fever, headache, joint aches, painful eye movements, anorexia, nausea, vomiting, lymphadenopathy

Infectious mononucleosis/Glandular fever:
Caused by Epstein-Barr virus (EBV) – low contagiousness. More common in ages 15-25 years. Spread by oral contact, usually saliva. Incubation unclear may be 7-10 days or up to 4 weeks.

Clinical features:
Prodromal (days 3-5) – fatigue/tiredness, headache, malaise, myalgias, anorexia, abdominal discomfort
Days 5 –15 – sore throat, enlarged tonsils, fever, tender lymph nodes, enlarged spleen (50%), jaundice (10%), morbilliform rash (10%)
Laboratory – elevated WBC count, lymphocytosis with many atypical lymphocytes, positive heterophil antibody absorption test (eg Monospot®), mild elevation in liver function tests

Differential diagnosis – viral hepatitis; streptococcal sore throat; HIV seroconversion illness; cytomegalovirus infection; leukaemia

Complications – chronic fatigue (most common); secondary infections; hepatitis, haemolytic anaemia, thrombocytopenia, meningoencephalitis; depression; renal failure; Guillain-Barre syndrome

Treatment:
Rest (usually bed rest); avoidance of alcohol
Acetaminiphen for symptoms
If severe  corticosteroids

Cytomegalovirus (CMV) Infection:
CMV is present in more than half of adults – the primary infection is usually asymptomatic or with a mononucleosis type illness  CMV then becomes latent  symptomatic reactivation can occur, usually in the immunosuppressed or times of stress. Spread by kissing, sexual intercourse, blood transfusions, organ transplant.

Clinical features:
Mononucleosis like illness, retinitis, hepatitis
Associated with Guillain-Barre syndrome
If immunosuppressed  enteritis, pneumonitis, generalised infection

Management:
Treatment only of serious; Ganciclovir, foscarnet

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