VIRAL HAEMORRHAGIC FEVERS

Viral infections associated with haemorrhagic manifestations Bacterial infection(malaria, meningococcal meningitis) Spirochetes infection

They are mainly rural and transmission is associated with poverty and poor medical facilities. Lassa fever is widespread in West Africa, where it accounts for 15% of adult hospital admissions and 50% of adults have antibodies. Ebola and Marburg viruses cause small epidemics but have high fatality rates. The most recent Ebola outbreak was in Angola in 2005. Kyasanur forest disease is a tick-borne viral haemorrhagic fever currently confined to a small focus India. Monkeys are the principal hosts. All of these viral illnesses except Ebola have mild self- healing forms.

Pathogenesis These viruses cause endothelial dysfunction with the development of leaky capillary syndrome. Bleeding is due to this and associated platelet dysfunction. Hypovolaemic shock and acute respiratory distress syndrome develop.

Clinical features All viral haemorrhagic fevers have similar non-specific presentations with fever, malaise, body pains, sore throat and headache. On examination conjunctivitis, throat injection, an erythematous or petechial rash, haemorrhage, lymphadenopathy and bradycardia may be noted.

In Lassa fever joint and abdominal pain are prominent. A macular blanching rash may be present but bleeding is unusual, occurring in only 20% of hospitalised patients. Haemorrhage is a late feature of established severe disease and most patients will present with earlier symptoms. Bradycardia and ECG abnormalities are common. Encephalopathy may develop. Deafness affects 30% of survivors.

Investigations CBP:There is leucopenia, thrombocytopenia GUE:proteinuria. In Lassa fever an LFT:aspartate amino transferase (AST) > 150 U/l is associated with a 50% mortality.

Diagnosis The clue to the viral aetiology will come from the travel and exposure history, so it is important to be aware of the incubation periods for these illnesses. Enquiry should be made about insect bites, particularly mosquitoes and ticks, hospital visits and attendance at ritual funerals (Ebola virus infection). The causative virus may be isolated, or antigen detected, in maximum security laboratories from serum, pharynx, pleural exudate and urine. The diagnosis of Lassa fever should be considered in non-endemic areas in patients presenting with fever within 21 days of leaving West Africa, particularly if they have organ failure or haemorrhagic features; most patients suspected of having a viral haemorrhagic fever in the UK turn out to have malaria.

Management It is important to exclude other causes of fever, especially malaria, typhoid and respiratory tract infections. Particular care must be taken with body fluids. Patients should be managed in isolation until a diagnosis is made. General supportive measures, preferably in a special unit, are required. Ribavirin is given intravenously (100 mg/kg, then 25 mg/kg daily for 3 days and 12.5 mg/kg daily for 4 days). Once haemorrhagic fever is confirmed, full pressure isolation is mandatory and good infection control practices will prevent further transmission.

Prevention Ribavirin has been used as prophylaxis in close contacts in Lassa fever but there are no formal trials of its efficacy.

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