A United Airlines plane was diverted to a remote gate at Los Angeles International Airport on Sunday after an ill passenger who had been to Africa raised concerns about Ebola. The passenger instead appeared to have motion sickness (Jonathan Alcorn/Reuters)

This is not a matter for the imagination: A little more than a month from now, several thousand Americans will have Ebola-like symptoms.

At the same time, millions of Americans will begin to set out from home for the busiest travel weekend of the year.

In a nation already jumpy with fear of the lethal virus that has killed more than 4,000 people in West Africa and one person in the United States — a Liberian man who flew to Texas — the confluence of the onset of flu season and the mass migration around Thanksgiving weekend figures to put people on edge.

Consider the similar symptoms.

Ebola: a 101-degree-or-higher fever, severe headache, muscle pain, weakness, vomiting, abdominal pain, diarrhea.

Thomas Frieden, director of the Centers for Disease Control and Prevention, provided an update Monday to the investigation into the spread of the Ebola virus to a nurse at a Dallas hospital. Frieden also apologized for his initial remarks about the nurse’s infection, which seemed to blame the nurse or other health care workers for the infection. (AP)

Flu: a 100-degree-or-higher fever, headache, body ache, fatigue, chills, nausea, vomiting, diarrhea.

With airline crews on alert, passengers scrutinizing each other for Ebola symptoms and special screening being established at major international airports, there is already evidence that one sickness can be mistaken for the other. As the flu begins its annual spread and holiday travel picks up in the coming weeks, the confusion is likely to lead to anxious moments.

About 43 million Americans will travel more than 50 miles from their home for Thanksgiving, based on the AAA survey from 2013. Most will drive — about 40 million — but more than 3 million will fly.

On average in recent years, between 50,000 and 60,000 people in the United States have come down with seasonal flu, according to the Centers for Disease Control and Prevention. Some years the number is far lower, and others it is much higher.

Last Thanksgiving week, of 5,306 people with flu symptoms who were tested, about 10 percent of them actually had the illness, according to the CDC. A 30-year federal survey on the flu found that February usually is the peak month but that there is a spike in December after the Thanksgiving travel.

Fear of Ebola sent emergency crews racing to meet a United Airlines flight into Los Angeles International Airport on Sunday after word that a passenger was vomiting and exhibiting flulike symptoms.

The fears were buttressed when it was learned that the passenger had flown through New York’s John F. Kennedy International Airport, destination for about 43 percent of those who fly to the United States from the three African nations hardest hit by Ebola, and that the passenger’s journey began in Africa.

The plane, with 148 people aboard, was diverted to a separate runway, where it was boarded by emergency workers wearing containment suits.

“Due to the concern and the nature of the patient’s illness, the Los Angeles Fire Department felt it very important to handle this following the CDC procedures,” Capt. Jamie Moore, a public information officer for the department, said at a news conference. “It has turned out that there was some miscommunication, that this person had been to the continent of Africa but not near West Africa. As a matter of fact, it was South Africa.”

Moore said the passenger appeared to have suffered from motion sickness.

Screening of international passengers for Ebola symptoms is scheduled to begin Thursday at Dulles International Airport, which receives 22 percent of the passengers who begin their travel in Liberia, Sierra Leone or Guinea. The enhanced screening also will be done at Chicago’s O’Hare International Airport, Hartsfield-Jackson Atlanta International Airport and Newark Liberty International Airport.

There are no direct U.S. flights from the three countries, so passengers who arrive at Dulles will be aboard flights from European hub cities.

The enhanced screening began Saturday at JFK Airport, where 91 travelers who began travel in those three African nations were given an Ebola-specific questionnaire and had their temperatures checked. Five of them were flagged for additional screening, said CDC Director Thomas Frieden. None of them had a fever and none of them had Ebola, Frieden said during a briefing with reporters Monday.

Mark Berman contributed to this report.