US resident dies after suspected Lassa fever infection in West Africa

US health officials are investigating the death of an Iowa resident as a suspected case of Lassa fever, a dangerous viral disease that is endemic in parts of West Africa but rarely seen in the US or Europe.

The patient returned to the US from West Africa early this month but was not sick while travelling, so the risk to fellow airline passengers is “extremely low,” officials with the US Centers for Disease Control and Prevention (CDC) said.

The patient, who died on Monday, had been hospitalised in isolation, and testing showed that they were presumptively positive for Lassa fever.

If the results are confirmed, it would be the ninth known case of Lassa fever since 1969 in travellers returning to the US from areas where the disease is found.

It’s also rare in Europe. There have been eight Lassa fever cases over the past decade, nearly all of them imported from abroad. The most recent was in France in May.

Patients are not believed to be infectious until they show symptoms, and the US CDC is assisting Iowa health officials to identify people who had contact with the patient after that point.

Lassa fever symptoms and spread

Symptoms are typically mild and include fever, fatigue and headache. Some people may develop vomiting, difficulty breathing, facial swelling and pain in the back, chest or stomach.

People identified as close contacts of the Iowa patient will be monitored for 21 days.

State and local health officials are working to learn how the patient, who they did not identify, became infected. Early information suggests the patient had contact with rodents in West Africa.

The virus is carried by rodents and spread to humans through contact with urine or faeces droppings of infected animals. In rare cases, it can be transmitted among people through direct contact with a sick person’s blood or bodily fluids, through mucous membranes or through sexual contact.

About 100,000 to 300,000 cases of Lassa fever and about 5,000 deaths occur in West Africa each year.