Bart Jansen

USA TODAY

Liberian authorities are threatening to prosecute the traveler who was diagnosed with Ebola in the United States because he denied on an exit questionnaire that he had been exposed to the often-fatal virus.

Health officials trained by the U.S. Centers for Disease Control and Prevention tested the patient, Thomas Eric Duncan, at the Monrovia airport for fever and found a normal 97.3-degree temperature.

The officials also asked Duncan whether he was exposed to Ebola through health-care or funeral services, according to CDC Director Tom Frieden. The same exit forms are used at airports across Liberia, Sierra Leone and Guinea, Frieden said.

"Individuals often don't know what their exposures may have been and not all individuals fully disclose what their exposures have been," Frieden said.

Liberia officials have threatened to prosecute Duncan for saying he hadn't been exposed.

"We expect people to do the honorable thing," said Binyah Kesselly, chairman of the board of directors of the Liberia Airport Authority in Monrovia. The agency took the case to the Ministry of Justice, which will formally prosecute it.

Ebola has infected 7,178 people and has killed 3,338 across West Africa, according to the World Health Organization.

During September, health officials in West Africa have pulled more than a dozen travelers with fevers from lines to get on planes, Frieden said.

"The vast majority of those didn't have Ebola," Frieden said. "They may have had malaria or cold or other things. But we're going to err on the side of safety."

But he said the risk of catching Ebola, which is transmitted through fluids such as blood only when the patient is feverish, will be eliminated when the outbreak is overcome in West Africa.

"It is not impossible that we will have other individuals come into the country and be diagnosed with Ebola," Frieden said.

Duncan didn't develop symptoms until four days after his flights to Dallas, so health officials insist that he wouldn't have been contagious. Likewise, sharing public transit or a community space with Duncan wouldn't count as exposure – and health officials aren't investigating workplaces or community locations for people exposed to Duncan.

"This is not like flu. It's not like measles," Frieden said. "It's not as spreadable."

Duncan flew from Liberia through Brussels and Washington to Dallas. United Airlines announced Wednesday the flight numbers 951 from Brussels to Dulles and flight 822 from Dulles to Dallas.

"We are ensuring our employees have this information and suggest that any customers who have concerns contact the experts at the CDC for further information," the airline said.

Customs and Border Protection officers are trained to look for sick travelers, who can be quarantined at major airports across the country. Frieden said the CDC would respond quickly if a sick traveler arrived, but that health officials are reluctant to cut off travel to countries hit by Ebola because that would make it harder to reach and treat those who are there.

"The best way to protect ourselves is not to seal off these countries," Frieden said.

Prosecuting an Ebola patient "on the precipice of death" is a "particularly harsh treatment," said Jens David Ohlin, professor of law at the Cornell Law School in New York. Still, he notes that an Ebola patient could deliberately lie in order to get better treatment abroad than is available in West Africa.

"Usually, compassion is the order of the day for Ebola patients," Ohlin said. "However, the Liberian government is clearly concerned that members of the public will not take their screening protocols seriously. If Ebola patients know that there are no legal consequences for lying on these forms, they will not take the screening seriously. And if travelers don't take the screening seriously, other countries will respond by closing air travel to Liberia."

Contributing: The Associated Press