Health officials say a New Jersey man has died after being diagnosed with Lassa fever — a frightening infectious disease from West Africa rarely seen in the United States.

The man arrived May 17 at New York City's JFK International Airport, returning from Liberia.

Health officials said he became critically ill after returning and died Monday evening.

They said they didn't think there was cause for public alarm. Lassa fever isn't spread through casual contact. About a half dozen other cases have been diagnosed in travelers before, none spread person-to-person.

As a precaution, officials with the U.S. Centers for Disease Control and Prevention are seeking anyone he had contact with recently, including health workers at two New Jersey hospitals and anyone seated near him on a recent flight from Morocco.