Health Alert: May 29, 2015

May 29, 2015

From: Donald T. Allegra, MD, ID Consultant

Re: Lassa Fever

On May 25th, the New Jersey Department of Health reported a death from Lassa Fever in a traveler who had come to the US from Liberia. He was asymptomatic when screened at JFK Airport on May 18th and then the next day had sore throat, fever, and fatigue. He presented to an emergency department in New Jersey and was apparently asked about travel and denied it, but then returned to the hospital 3 days later, much sicker, and eventually died. The New Jersey case is the 6th case of Lassa reported in the US in returning travelers since 1969.

Lassa Fever is in the viral family of hemorrhagic fevers like Ebola, but much less serious. It was first discovered in 1969 and the name comes from the town in Nigeria where the first cases occurred. It has a mortality rate of only about 1% compared to as high as 70% with Ebola. It is most common in West Africa in Liberia, Sierra Leone, Guinea, and Nigeria, but other countries in the area also have reported cases. There are estimated to be 100,000 to 300,000 cases a year in West Africa with about 5000 deaths.

The virus is transmitted by the multimammate rat, which is very common in both rural and urban areas of West Africa. It often inhabits homes and scavenges for human food left unprotected. The virus is transmitted by direct contact with urine or droppings of these infected rodents or by aerosols of tiny particles contaminated with infected rodent droppings. The incubation period is 1-3 weeks and 80% of patients present with mild non-specific symptoms such as fever, malaise, weakness, and headache. Symptoms are varied and non-specific which makes a clinical diagnosis difficult. 20% of patients can develop more serious illness including bleeding, respiratory distress, nausea/vomiting, and encephalitis or inflammation of the brain. Death usually comes from multi-organ system failure. The most common complication is deafness which can occur even in mild cases and is often permanent. The anti-viral drug, Ribavirin, has been used successfully in treatment and is most efficacious when used early in the illness. There is no vaccine available at this time.

Person to person transmission has never been documented in the US and does not occur with casual contact. It is felt that direct contact with blood or body fluids through skin cuts, mucous membranes, or sexual contact is necessary to spread the virus.

There is no expectation that Lassa will present a risk to the US population or result in secondary cases such as happened with Ebola. However, the lessons to take away from this recent incident is that we live in a very interconnected world where citizens of any country are within a 24 hour reach of our 3 major airports. Liberia has been declared free of Ebola but Sierra Leone and Guinea still are having cases and we have to maintain our vigilance for Ebola and other infectious diseases.