A Minnesota man who flew home from West Africa late last month has been diagnosed with Lassa fever, a viral infection that rages in Africa but is rarely seen in the United States.
Now state and federal health authorities are contacting passengers and crew from the same flights to see if they also were infected.
The case — the first in the United States since 2010 — was detected when the man went to a Minnesota hospital March 31 with fever and confusion.
The Lassa virus is not spread by casual contact. It is transmitted via bodily fluids such as blood or saliva. So health authorities do not suspect that fellow travelers or other Minnesotans have contracted the infection.
In West Africa, the disease infects as many as 300,000 people each year, killing 5,000. The Lassa virus is similar to the dreaded Ebola virus in that it can cause severe hemorrhagic fevers, though its fatality rate is considerably lower.
The infected man changed planes in New York City en route from West Africa to the Twin Cities. All the travelers and health care providers he encountered will be contacted.
The appearance of a rare virus — even one with a low public health threat — raises national concern, because it reveals the ease with which dangerous pathogens can enter the country in an era of increased global travel.
“This imported case is a reminder that we are all connected by international travel,” said Dr. Tom Frieden, director of the U.S. Centers for Disease Control and Prevention. “A disease anywhere can appear anywhere else in the world within hours.”
The CDC confirmed the virus through a blood test.
The identity of the man, his flights, and the treating hospital were not disclosed by the Health Department by Friday afternoon. But officials said he is recovering.
“The hospital has done an excellent job of caring for the patient and taking all necessary measures to ensure the safety and protection of hospital staff, visitors and patients,” said Dr. Ed Ehlinger, commissioner of the Minnesota Department of Health.
Lassa virus is designated with a biosafety level 4, meaning researchers in the U.S. would be required to wear protective suits and be in air-controlled rooms when working with any samples. There are only a handful of BSL4 labs in the nation where the virus could be safely handled.
Lassa virus is primarily carried by rodents in West Africa and spreads to humans through contact with their urine or droppings. Most infections do not result in symptoms.
Deaths occur in 1 to 2 percent of infections, but that is partly because of poorer symptom management in Africa, said Dr. Aaron DeVries, a medical epidemiologist with the Health Department. Deaths would probably be lower if there ever were a U.S. outbreak because of adequate management of dehydration, blood pressure and other symptoms, he said.
Seven other Lassa fever cases, all travel related, have been identified in the United States. The last was in Pennsylvania four years ago, when a 47-year-old Liberian man visited the country after sleeping in his rat-infested rural village, according to a CDC case report. His initial symptoms of fever and chills were mistaken for a malaria infection, and he started taking antibiotics before departing for the U.S.
A review of 140 people in contact with the man in that case found no other people who were infected.
DeVries credited the physician who treated the man in the latest case in Minnesota. The doctor immediately notified state health officials after hearing the man’s symptoms and travel history and having suspicions. Testing confirmed the Lassa infection April 3, DeVries said, making this the first known case of the viral infection in Minnesota.