John Nides and his wife had buckled up for the trip home from New York on March 31 when a passenger boarded Delta Flight 2921 who needed help from a flight attendant to navigate the walkway, according to Nides, and was garbling his words.
"Everybody thought this guy was drunk," Nides said.
The passenger, who sat right across the aisle from Nides and his wife, was infected with Lassa virus, a rat-born infection common in west Africa that hasn't been detected in the United States since 2010. Within days, the Minnesota Department of Health and the Centers for Disease Control and Prevention had launched an investigation to make sure the virus hadn't spread to others on the flight or, later, to the staff at a Twin Cities hospital where he was treated.
There is no sign that Lassa fever struck the other passengers - the virus spreads through blood and saliva, not casual contact. But the incident is raising questions about what protections are in place to prevent passengers with contagious diseases from boarding commercial flights and, through international travel, potentially spreading viruses far and wide.
"How do you let a person like that on an airplane?" Nides asked. "This guy was physically sick. This guy needed help getting on the plane."
Nides himself is still bothered by what happened on Delta 2921. He was contacted by government health officials April 5, quizzed about his proximity to the infected man, and asked to take his temperature twice daily.
Federal officials agreed that the case raised concerns about public health safety when they reported the infection to the public April 4. CDC Director Dr. Tom Frieden called it a reminder that "a disease anywhere can appear anywhere else in the world within hours."
Ever since the well-documented SARS and H1N1 influenza outbreaks that crossed international borders a few years ago, airlines and airports have worked with the CDC to promote awareness about the risks of infected passengers. U.S. Customs and Border Protection agents working at airports are trained to identify passengers known by federal public health officials to have communicable diseases, and to contact on-site medical personnel to check on them.
Airlines that identify potentially infected passengers are not required by federal law to keep them off flights, but pilots are required to notify health officials before they land if any passengers exhibit fevers that have lasted more than 48 hours or are accompanied by rashes, jaundice or swelling.
Airlines have worked with the CDC to develop their own protocols on how to respond if ticket agents, flight attendants or others have concerns about passengers, said Katie Connell, a spokeswoman for the Airlines for America trade group.
"A traveler who is identified as a health risk to others by public health authorities may be denied boarding," she said.
At Delta, if workers have concerns they are supposed to contact an emergency medical contractor at the University of Pittsburgh who assesses the situation and whether a passenger is fit to fly.
Federal officials said none of these rules were overlooked in the Lassa fever incident.
The infected man was coming from Nigeria when he reached a Customs checkpoint early on March 31 at JFK airport in New York, according to a statement provided by Customs spokesman Anthony Bucci. "The traveler did not exhibit any outward signs of illness and was subsequently admitted."
The fever was confirmed only after the plane landed in Minneapolis-St. Paul and the infected man was hospitalized. It's the first recorded case of Lassa virus in Minnesota.
A Delta spokeswoman declined to comment on the man's condition, but CDC spokeswoman Candice Burns Hoffmann said he didn't exhibit obvious signs of fever during the trip.
"Even if he needed assistance on the plane," she said, "this could have been due to something other than an infectious disease."
Nides disagreed. While he doesn't know whether the man appeared ill before he boarded, he said a flight attendant had to hold the passenger by the shoulder to guide him to his seat. The man also leaned forward against the seat back in front of him, Nides recalled, and flight attendants repeatedly checked on him in flight. When he dropped a piece of paper, he was too weak to pick it up, Nides said.
As a frequent business traveler who sells reading glasses, Nides has had some odd experiences on airplanes. He appeared in news coverage in 2009 after being stuck on a Sun Country plane that sat on the tarmac in New York for hours instead of returning to its gate. He said he's grateful this episode didn't involve a more lethal virus that could spread through the air.
"This is just a warning," he said.
In west Africa, 300,000 people are diagnosed with Lassa infections each year; others carry the virus without symptoms. The mortality rate from known infections is 1 percent to 2 percent, but health officials believe it would be lower in the U.S. due to better medical care.
In the days after the March 31 flight, the CDC reached out to people who came in close contact with the infected man and asked them to monitor their health and body temperatures.
Nides told them he didn't have thermometers at his Mendota Heights, Minn., home. The next day, he said, a state epidemic intelligence officer hand-delivered two of them.