New Jersey officials are trying to track down health care workers and others who had contact with a man who died of an infectious disease that is rarely seen in the United States.

The U.S. Centers for Disease Control and Prevention said Monday that a man had died of Lassa fever, days after returning from a trip to West Africa.

University Hospital in Newark said Tuesday the man had been transferred there Saturday from another hospital because it could deal with viral hemorrhagic fevers. The hospital said in a statement that it is reviewing whether any of its employees were at risk of exposure to the virus.

The disease is far less likely to be fatal than Ebola and does not spread through casual contact but rather through contact with the blood, feces or vomit of an infected person, or the urine or droppings of infected rodents. About a half-dozen cases have turned up in the United States, including one in Minnesota last year.

Officials have not released the name of the victim or the other hospital where he was first treated.

The New Jersey Department of Health said it is trying to find people who came into contact with him so local health officials can monitor them for 21 days to ensure they do not develop symptoms.

The man arrived at New York City's JFK International Airport on May 17 after traveling in West Africa.

Officials say he did not have symptoms while on the plane but developed a sore throat and lethargy later and went to a hospital.

The CDC said Sunday that his airline would be notified so people who sat close to him on his flight from Morocco could also be monitored.

Lassa fever was named after a Nigerian town where Western-trained doctors first noted it in 1969. An estimated 100,000 to 300,000 infections occur in West Africa each year, including about 5,000 deaths. In some areas of Sierra Leone and Liberia, 10 to 15 percent of people admitted to hospitals every year have Lassa fever.

The disease can cause a wide range of symptoms, including sore throat, back and abdominal pain, facial swelling, vomiting, hearing loss and tremors.