In this Oct. 16 file photo released by U.S. Customs and Border Protection, U.S. Coast Guard Health Technician Nathan Wallenmeyer, left, and CBP supervisor Sam Ko, right, conduct prescreening measures on a passenger who has arrived from Sierra Leone at O'Hare International Airport's Terminal 5 in Chicago. (Melissa Maraj/AP)

Four passengers who flew into Dulles International Airport recently were taken to a local hospital after enhanced airport screening alarmed the Centers for Disease Control, the Department of Homeland Security said Tuesday.

The agency and the CDC provided no details on the hospital visits or whether the passengers were admitted to the hospital. Spokespeople for the two Northern Virginia hospitals closest to the airport said they did not receive the passengers.

“We have no patients,” said Reston Hospital Center nursing supervisor Kim Wilfred.

“I’m not aware of anything like that, and I would be aware,” said Tony Raker at Inova Fairfax Hospital.

The CDC and DHS could not explain the discrepancy.

Here's how the Metropolitan Washington Airports Authority at Dulles International Airport is handling the stricter screening of passengers arriving from Guinea, Sierra Leone and Liberia. (Trey Yingst/The Washington Post)

A person familiar with the screening at Dulles said that a 13-year-old boy and his mother were taken to a hospital last Thursday after the CDC became concerned about their symptoms. The source, who asked not to be named because of the sensitivity surrounding Ebola fears, said two other passengers also were taken to a hospital over the weekend. The person was unable to name the hospital, and said that all four passengers apparently were released after further testing at the hospital.

Since enhanced screening began in John F. Kennedy International Airport in New York on Oct. 11 and at four other airports five days later, 521 passengers who began their travel in Guinea, Sierra Leone or Liberia have been subject to enhanced screening that includes an Ebola questionnaire and having their temperature taken. Fever is an early symptom of Ebola.

An additional 41 passengers also were subject to screening for unspecified reasons, homeland security said.

The numbers indicated that the number of people arriving from the three Ebola-hit countries has dropped significantly below the 150-per-day estimates of the CDC last week. They suggest that about 80 people are coming into the country daily.

All 562 of them were subjected to temperature taking, and just three showed abnormally high temperatures. Twenty-eight others received additional CDC testing at the five airports.

At JFK, where screening first began, 567 people were screened, two people had high temperatures, 15 people got an advanced screening and none were taken to hospitals.

At Newark International Airport, where enhanced screening began Thursday, 37 had their temperatures taken, none showed a fever, five got additional CDC screening and none were taken to a hospital.

(Ian Robinson/The Washington Post/Source: Department of Homeland Security)

At Chicago O’Hare International Airport, 18 were screened, none had high temperatures or faced CDC screening, and none were taken to a hospital.

At Atlanta’s Hartsfield-Jackson International Airport, 27 received enhanced screening, none had fevers, one got additional CDC screening and no one was taken to a hospital.

At Dulles, 113 were screened, one had a fever, 28 received advanced CDC screening and four were taken to “a local hospital.”

Meanwhile, travelers from those African nations to the United States will now be required to enter the country through one of the five airports with the enhanced screening under restrictions announced Tuesday.

The new rule, which goes into effect Wednesday, closes what had been a relatively small gap in the stricter screening measures rolled out earlier this month. The enhanced screening targets people who have visited or reside in Guinea, Liberia or Sierra Leone, the nations where the virus has hit hardest, killing more than 4,500 people.

There are no direct U.S. flights from the three countries. At the outset of the crisis, federal officials said that an average of 150 people arrived in the United States from those countries each day, often landing after changing planes at European hubs such as Brussels or London. An estimated 94 percent of them flew into the five gateway airports: John F. Kennedy International Airport in New York; Washington Dulles International Airport; O’Hare International Airport in Chicago; Hartsfield-Jackson International Airport in Atlanta; and Newark Liberty International Airport near New York.

But this meant that 6 percent of travelers — or roughly nine people a day, according to numbers from the Centers for Disease Control and Prevention — would have avoided the measures meant to catch potential Ebola cases before the passengers leave the airport.

“We are continually evaluating whether additional restrictions or added screening and precautionary measures are necessary to protect the American people and will act accordingly,” Jeh Johnson, secretary of homeland security, said in a statement Tuesday.

Under the enhanced screening protocol, if the passenger has a fever or responds with a “yes” to any of the questions on a special Ebola questionnaire, the passenger is sent to on-site CDC personnel for the additional assessment.

A traveler viewed as at risk is referred to public health authorities.