The ease and frequency of international travel makes viruses no longer geographically limited. A case of Lassa fever was reported in Minnesota earlier this week. The virus is common in West Africa, but extremely rare in the United States, with only seven cases ever being reported. Although the virus is not easily spread, the Centers for Disease Control and Prevention (CDC) is still taking serious precautions to ensure that it will not spread further.

On March 31st, a man in Minnesota fell ill after returning from a trip to West Africa. He was hospitalized with fever and confusion, and blood tests later confirmed that he had Lassa Fever, according to NBC News. There have been no details released about the man’s age or whereabouts, but officials are working with the airline he flew in to identify other passengers that he may have come into close contact with. The patient flew from West Africa to New York City, and then to Minneapolis. The CDC is looking to verify that no other passengers had contracted the virus from him during the duration of the flight. Dr. Martin Cetron, director of the CDC’s division of global migration and quarantine, ensures that the chances that the patient spread the virus during the flight are extremely low. “Given what we know about how Lassa virus is spread to people, the risk to others and members of the public is extremely low,” Cetron told NBC. The virus is spread between humans by direct contact with a sick person’s blood or body fluids, or through contact with mucous membranes or sexual contact.

Lassa fever is common in West Africa, where it affects about 100,000 to 300,000 people each year. There are about 5,000 annual deaths attributed to the virus. There are, however, only seven recorded cases of Lassa fever occurring in the United States. The last case occurred in Pennsylvania in 2010. Symptoms of the virus include fever, weakness, sore throat, nausea and vomiting, diarrhea, cough, and headache. In about 20 percent of cases, patients will exhibit hemorrhaging in their gums, eyes, or nose. They may also experience facial swelling, hearing loss, and encephalitis. The most common complication associated with Lassa fever is deafness. In most extreme cases, death can occur from Lassa fever. This may happen as quickly as two weeks after the onset of symptoms.

Source: Yusuph, H. Lassa fever: epidemiology, clinical feature, and social consequences. BMJ. 2003.