Clinical illness

· In clinical illness the onset is gradual, with fever, malaise, headache, sore throat, cough, nausea, vomiting, diarrhoea, myalgia (painful muscles), and chest and abdominal pain. The fever may be either constant or intermittent with spikes. Inflammation of the throat and eyes is commonly observed.

· In severe cases, hypotension or shock, pleural effusion (fluid in the lung cavity), haemorrhage, seizures, encephalopathy (dysfunction of the brain) and swelling of the face and neck are frequent. Approximately 15% of hospitalized patients die. The disease is more severe in pregnancy, and fetal loss occurs in greater than 80% of cases.

· Hair loss and loss of coordination may occur in convalescence. In addition, deafness occurs in 25% of patients, with only half recovering some function after one to three months. Immunity to reinfection occurs following infection, but the length of this period of protection is unknown.