A New Jersey man who was hospitalized after returning from West Africa died last night from a Lassa virus infection, the second case to be detected in the United States since 2014, the US Centers for Disease Control and Prevention (CDC) said in a statement.
The CDC said though Lassa fever is a viral hemorrhagic disease similar to Ebola and common in West Africa, it is less likely to be fatal and spread from person to person. It can cause severe disease, however, as it did in the New Jersey man, and efforts are under way to identify the man's contacts.
Those who were in close contact will undergo 21-day symptom monitoring.
Man didn't have fever during travel
On May 17 the man traveled from Liberia to Morocco to JFK International Airport in New York City. The man didn't have a fever when he left Liberia, didn't have symptoms on the plane, and when his temperature was taken upon his arrival in the United States, he didn't have a fever.
The following day he went to a New Jersey hospital with a sore throat, fever, and fatigue. According to the hospital, he was asked about his travel history and did not indicate travel to West Africa.
He was sent home the same day, but returned on May 21 when his symptoms worsened. The hospital transferred him to a treatment center that is prepared to treat viral hemorrhagic fevers, where he was in appropriate isolation and died. Samples submitted the CDC were positive for Lassa fever, but negative for Ebola and other viral hemorrhagic fever organisms.
According to the New Jersey Department of Health (NJDOH), the 55-year-old man was placed in isolation when he was admitted to the hospital on May 21 with a fever and a sore throat. His condition continued to decline during his hospital stay.
The NJDOH said it is working with hospital officials to identify all close contacts, including health workers, family members, and others, out of an abundance of caution.
The man's illness is the sixth known Lassa fever case, not including convalescent ones, in a traveler to the United States reported since 1969. The most recent illness was detected in a Minnesota man who had returned from West Africa in April 2014.
Threat to public thought to be low
West Africa has about 100,000 to 300,000 cases of Lassa fever each year, and about 5,000 of the infections are fatal. The Lassa virus is carried by rodents and spreads to humans through contact with rodent urine and droppings.
In humans, the disease can be transmitted through direct contact with a sick patient's blood or body fluids or mucous membranes, or through sexual contact.
The disease is thought to peak in West Africa in the dry season months of late winter.
Christina Tan, MD, MPH, New Jersey's state epidemiologist, said in the NJDOH statement, "Given what we know about how Lassa virus spreads to people, we think the risk to the public is extremely low."
May 25 CDC statement
May 25 NJDOH statement
Apr 4, 2014, CIDRAP News story "Minnesota Lassa fever case first in US since 2010"