EBOLA IN THE AIR? A nightmare that could happen

By Elizabeth Cohen, Senior Medical Correspondent

No one will be allowed to leave their homes for three days, and volunteers will be allowed to go door to door to educate people on the Ebola virus. Health officials say the Ebola outbreak in West Africa is the deadliest ever. More than 4,700 cases have been reported since December, with more than 2,400 of them ending in fatalities, according to the World Health Organization. Police in Freetown, Sierra Leone, guard a roadblock Friday, September 19, as the country began enforcing a three-day nationwide lockdown. No one will be allowed to leave their homes for three days, and volunteers will be allowed to go door to door to educate people on the Ebola virus. Health officials say the Ebola outbreak in West Africa is the deadliest ever. More than 4,700 cases have been reported since December, with more than 2,400 of them ending in fatalities, according to the World Health Organization.

(CNN) -- Today, the Ebola virus spreads only through direct contact with bodily fluids, such as blood and vomit. But some of the nation's top infectious disease experts worry that this deadly virus could mutate and be transmitted just by a cough or a sneeze.

"It's the single greatest concern I've ever had in my 40-year public health career," said Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. "I can't imagine anything in my career -- and this includes HIV -- that would be more devastating to the world than a respiratory transmissible Ebola virus."

Osterholm and other experts couldn't think of another virus that has made the transition from non-airborne to airborne in humans. They say the chances are relatively small that Ebola will make that jump. But as the virus spreads, they warned, the likelihood increases.

Every time a new person gets Ebola, the virus gets another chance to mutate and develop new capabilities. Osterholm calls it "genetic roulette."

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As of Friday, there have been 4,784 cases of Ebola, with 2,400 deaths, according to the World Health Organization, which says the virus is spreading at a much faster rate now than it was earlier in the outbreak.

Ebola is an RNA virus, which means every time it copies itself, it makes one or two mutations. Many of those mutations mean nothing, but some of them might be able to change the way the virus behaves inside the human body.

"Imagine every time you copy an essay, you change a word or two. Eventually, it's going to change the meaning of the essay," said Dr. C.J. Peters, one of the heroes featured in "The Hot Zone."

That book chronicles the 1989 outbreak of Ebola Reston, which was transmitted among monkeys by breathing. In 2012, Canadian researchers found that Ebola Zaire, which is involved in the current outbreak, was passed from pigs to monkeys in the air.

Dr. James Le Duc, the director of the Galveston National Laboratory at the University of Texas, said the problem is that no one is keeping track of the mutations happening across West Africa, so no one really knows what the virus has become.

One group of researchers looked at how Ebola changed over a short period of time in just one area in Sierra Leone early on in the outbreak, before it was spreading as fast as it is now. They found more than 300 genetic changes in the virus.

"It's frightening to look at how much this virus mutated within just three weeks," said Dr. Pardis Sabeti, an associate professor at Harvard and senior associate member of the Broad Institute, where the research was done.

Even without becoming airborne, the virus has overwhelmed efforts to stop it.

The group Doctors Without Borders says Monrovia, Liberia, needs 1,000 beds for Ebola patients but has only 240, and it has had to turn patients away, sending them back to neighborhoods where they could infect more people.

This week, a Pentagon spokesman said the United States is sending a 25-bed field hospital to Monrovia.

"A 25-bed hospital with nobody to staff it? That's not the scale we need to be thinking about," Le Duc said. "It's an absolute embarrassment. When there was a typhoon in the Philippines, the Navy was there in 48 hours and had billions of dollars in resources."

Osterholm commended groups like Doctors Without Borders but said uncoordinated efforts by individual organizations are no match for Ebola spreading swiftly through urban areas.

"This is largely dysfunctional. Nobody's in command, and nobody's in charge," he said. "It's like not having air traffic control at an airport. The planes would just crash into each other."