NEW YORK — U.S. health officials on Thursday warned Americans not to travel to the three West African countries hit by an outbreak of Ebola.
The travel advisory applies to nonessential travel to Guinea, Liberia and Sierra Leone, where the deadly disease has killed more than 700 people this year.
"The bottom line is Ebola is worsening in West Africa," said Dr. Tom Frieden, director of the Centers for Disease Control and Prevention, who announced the travel warning.
He called Ebola "a tragic, dreadful and merciless virus."
The purpose of the travel warning is to not only protect U.S. travelers, but limit their use of overburdened clinics and hospitals for injuries or other illnesses, he said.
Also Thursday, the White House said it is looking into options for bringing back two American aid workers sick with Ebola in Liberia. It would be the first time the disease was brought into the country.
For more than a month, CDC has advised travelers to simply take precautions when in the outbreak region. Thursday's alert is the highest-level. The World Health Organization, however, has not issued a similar travel warning for the West Africa region. The last time the CDC issued a high-level warning was in 2003 because of a SARS outbreak in Asia.
The current outbreak is the largest since the disease first emerged in Africa nearly 40 years ago. The virus is contagious and is spread by direct contact with blood or bodily fluids from a sick person. Ebola can't be spread like flu through casual contact or breathing in the same air.
Experts estimate that in this outbreak, about 60 percent of the people who have gotten sick with Ebola have died — a frightening fatality rate that is among the highest of any disease. There is no vaccine and no specific treatment for it.
The two American aid workers in Liberia diagnosed with Ebola are Dr. Kent Brantly and Nancy Writebol, who work for North Carolina-based groups. Writebol was getting an experimental treatment, the mission groups said Thursday.