WEDNESDAY, Oct. 15, 2014 (HealthDay News) -- The second nurse at a Dallas hospital to be diagnosed with Ebola flew on a domestic, commercial airline flight on Monday evening -- less than 24 hours before she reported symptoms to hospital staff, federal health officials said Wednesday.
Health officials said the risk is low that Amber Joy Vinson, 26, exposed her fellow passengers to Ebola during Frontier Airlines flight 1143 from Cleveland to Dallas/Fort Worth.
"The fact that patient number two did not have a fever until the next day, did not have nausea or vomiting on the plane, suggests to us that the risk to any around that individual on the plane would have been extremely low," Dr. Tom Frieden, director of the U.S. Centers for Disease Control and Prevention, said during a Wednesday news conference.
U.S. health experts have maintained that Ebola can only be transmitted by a person who is exhibiting symptoms, such as fever or vomiting.
Nonetheless, the CDC is working with Frontier to identify and notify all 132 passengers on the flight, which landed in Dallas on Monday at 8:16 p.m. CT, as an "extra margin of safety," Frieden said.
Vinson is ill but clinically stable in isolation at Texas Health Presbyterian Hospital in Dallas, Frieden said. She will be transferred to Emory University Hospital in Atlanta, which already has successfully treated two Ebola survivors, Dr. Kent Brantly and Nancy Writebol. Both medical missionaries, Brantly and Writebol became infected while working to combat the Ebola outbreak in West Africa.
Vinson already was in Ohio when she learned that the first nurse infected at Texas Health Presbyterian Hospital, Nina Pham, had been diagnosed with Ebola. Vinson violated CDC safety guidelines by boarding the flight back to Dallas, Frieden said.
"Because at that point she was in a group of individuals known to have exposure to Ebola, she should not have traveled on a commercial airline," he said.
A self-check revealed prior to boarding that her temperature was elevated, at 99.5 degrees, Frieden said. Even though Vinson had not reached the fever threshold of 100.4 degrees, her temperature, combined with her potential exposure to Ebola, should have kept her off the plane, Frieden said.
"By both of those criteria, she should not have been on that plane," Frieden said. But, he added, "She did not vomit. She was not bleeding. So the level of risk to people around her would be extremely low."
Anyone who was on the flight is being asked to call 1 800-CDC INFO (1-800-232-4636).
"The health care worker [Vinson] exhibited no signs or symptoms of illness while on flight 1143, according to the crew," the CDC said in a statement Wednesday. The plane was cleaned after landing in a manner "consistent with CDC guidelines prior to returning to service the next day," Frontier added in a statement. The aircraft has since been removed from service.
Public health officials believe that both Vinson and Pham became infected while treating Liberian national Thomas Eric Duncan in the days following his admission to Texas Health Presbyterian Hospital on Sept. 28, but prior to his official diagnosis with Ebola on Sept. 30, Frieden said.
Duncan, who died at the hospital on Oct. 8, was the first person diagnosed with Ebola in the United States. He became infected in Liberia before arriving in Dallas on Sept. 20.
"Our investigations increasingly suggest that the first several days before the patient [Duncan] was diagnosed appear to be the highest risk period," Frieden said. "These two health care workers both worked on those days and both had extensive contact with the patient when the patient had extensive production of body fluid because of vomiting and diarrhea."
If that's the case, the infection occurred before the CDC arrived on the scene in response to Duncan's Ebola diagnosis and could help direct infection-control measures, Frieden said.
"In those first several days in the hospital, a variety of forms of personal protective equipment were used," he said. "There are several ways to use personal protective equipment safely. It's critical that be done consistently and correctly, and that's one of the areas of active investigation."
Vinson's preliminary Ebola diagnosis was made after a test late Tuesday at the Texas public health laboratory in Austin. A second test that's expected to confirm the diagnosis on Wednesday will come from the U.S. Centers for Disease Control and Prevention.
Officials have identified three people other than the passengers on the flight from Cleveland who may have been exposed to Ebola through Vinson, Frieden said. All will be monitored, he said.
Health officials also are monitoring one person who could have been exposed through Pham, as well as 76 health care workers potentially exposed while caring for Duncan at the Dallas hospital. The CDC is working with state and local officials to track the movement of these people, Frieden said.
Pham, 26, was in improved condition Wednesday, and will remain at Texas Health Presbyterian for treatment in isolation, Frieden said.
Officials also are still monitoring 48 people who may have been exposed to Ebola through contact with Duncan prior to his hospitalization. But Frieden expressed optimism Tuesday that this first pool of potential exposures will emerge without a single infection.
Two-thirds of the 21-day maximum incubation period for Ebola has passed and no one from that group has developed any symptoms, he said Tuesday.
"They've now passed through the highest risk period and it's increasingly unlikely that they will develop Ebola," he said.
Liberia, Duncan's native country, is one of three West African nations -- the others are Guinea and Sierra Leone -- that have been ravaged since the spring by the worst outbreak of Ebola in history.
The Ebola epidemic in West Africa continues to spiral out of control, with the World Health Organization warning there could be up to 10,000 new cases a week within two months.
The WHO updated its Ebola statistics on Tuesday, reporting that 4,447 people have died out of 8,914 reported cases of infection. Nearly all cases and deaths have occurred in Guinea, Liberia and Sierra Leone.
To allay fears of hospital workers in the United States, Frieden said Tuesday that he was establishing a CDC Ebola response team that will be sent to "any hospital anywhere in this country with a confirmed case of Ebola."
"We will put a team on the ground within hours, with some of the world's leading experts" in infection control, laboratory science, protective equipment and management of Ebola units, Frieden said.
For more on Ebola, visit the U.S. Centers for Disease Control and Prevention.