A 55-year-old man who recently visited West Africa returned home to New Jersey but died there on Monday evening from a viral disease called Lassa fever, which can produce symptoms similar to Ebola but is less contagious, health officials said.
Although Lassa fever is common in West Africa, it is rare in the United States — there have been only five other cases of the virus in this country in the last half century, according to the Centers for Disease Control and Prevention. The virus doesn't spread through casual contact, or through the air, and there has never been a case of person-to-person transmission of Lassa fever in the U.S., the CDC said.
"Given what we know about how Lassa virus spreads to people, we think the risk to the public is extremely low,” said Dr. Tina Tan, an epidemiologist at the New Jersey Department of Health, said in a statement.
The man had recently visited Liberia, and arrived back in the United States on May 17 at John F. Kennedy International Airport in New York City. He did not have a fever or other symptoms before his travel or when he landed, the CDC said. [10 Deadly Diseases That Hopped Across Species]
But the next day, the man developed a fever, sore throat and fatigue, and went to a hospital in New Jersey. Although the patient was asked about his travel history, he did not say that he had been to West Africa, the CDC said.
The patient was sent home, but returned to the hospital on May 21 with more severe symptoms, and was put in isolation. Yesterday (May 25), blood samples from the man tested positive for Lassa fever (and negative for Ebola), the CDC said. The patient died later that day.
Lassa fever belongs to a group of viruses known as "viral hemorrhagic fevers," which can cause problems with the body's blood vessels that lead to increased bleeding. Ebola is another type of hemorrhagic fever.
But Lassa fever is usually less fatal than Ebola — only 1 percent of Lassa fever cases result in death, compared with about 70 percent of Ebola cases, the CDC said.
Lassa fever is more common in West Africa than Ebola — there are about 100,000 to 300,000 cases of Lassa fever in the region each year. (Until 2014, Ebola illnesses were rare, but a recent outbreak has caused nearly 27,000 cases of Ebola there in the last year.) However, Lassa fever is less likely than Ebola to spread from person-to-person.
Lassa fever is usually transmitted to people in West Africa from contact with rodent urine or droppings, which carry the virus, the CDC said. Although the risk is low that anyone else caught the virus from the New Jersey patient, health officials are identifying the people who had close contact with the patient and will monitor them for symptoms for 21 days.