Bart Jansen, USA TODAY
Health officials say the risk of spreading Ebola through airline travel is low, even though a man who traveled from Liberia to the United States was diagnosed with the disease, because travelers from affected countries are screened before boarding and the often fatal disease is not transmitted when an infected person has no symptoms.
The Ebola outbreak in West Africa, which has infected 6,500 people and killed 3,000, has prompted screening of travelers for fever at airports across Liberia, Sierra Leone and Guinea, and in Lagos, Nigeria.
The patient diagnosed Tuesday in Dallas had flown Sept. 19 from Liberia and arrived in the USA on Sept. 20. He had passed the fever screening and developed symptoms only on Sept. 24. He sought treatment Sept. 26.
Tom Frieden, director of the Centers for Disease Control and Prevention, says health officials are tracking a handful of the man's contacts in the United States.
"At this point, there is zero risk of transmission on the flight," Frieden said. "It does not spread from someone who doesn't have fever or other symptoms."
Ebola is not spread through breathing the air, like influenza or tuberculosis. Ebola is spread by direct contact with blood, mucus or other fluids from an infected person.
The disease usually incubates in an infected person for two to 21 days. Initial symptoms include fever, weakness, muscle pain, headache and sore throat, followed by vomiting, diarrhea, rash and bleeding.
The World Health Organization and the International Civil Aviation Organization, a branch of the United Nations that recommends policies for airlines, are reluctant to halt flights to entire regions because of the importance of travel and getting health care workers to the affected area.
"The risk of a traveler becoming infected with Ebola virus during a visit to the affected areas and developing the disease after returning is extremely low, even if the visit included travel to areas where primary cases have been reported," the WHO said in a statement.
WHO cites Nigeria as nearing an end to its outbreak because of quickly isolating its patients and tracing their contacts.