Ebola virus disease - also called ebola hemorrhagic fever - has been spreading rapidly in West Africa since February of this year. As of the end of July, the World Health Organization reports 887 deaths out of 1603 known cases, making it the largest outbreak in the history of the disease, in terms of both number of cases and geographical reach, which includes Liberia, Guinea, and Sierra Leone.
The ebola virus is trasmitted via bodily fluids, including blood, saliva, sweat, and feces, or via the soiled linens or needles used by an infected person. The virus can also stay alive for several days on surfaces touched by infected bodily fluids. There are no documented reports of airborne transmission. It is not clear how the virus first appears in humans, but it may be through infected animals, such as bush meat, which is the cooked or smoked remains of various wild animals commonly eaten in West Africa. The disease can spread quickly when family members take care of infected persons without taking proper precautions, and themselves become infected. In addition, the dead bodies of infected persons are still infectious, meaning that transmission can occur through embalming, or through the common African practice of washing the deceased before burial. In fact, the WHO is working with African officials to communicate to local residents that touching the body of someone who has died of Ebola virus is the worst thing to do, as bleeding, vomiting, and diarrhea are common shortly before death, and can transmit the virus to anyone who touches the body. In some communities, relief workers who are trained and have the equipment to bury an infected body safely are being prevented from doing so by angry locals, who don't understand the risk, and feel that their traditions are being interfered with.
What are the risks to the general population in bringing infected health care workers back to the United States for care? Virtually nil. The news coverage shows quite clearly the precautions being taken to prevent transmission to those in direct contact with Dr. Kent Brantly and Nancy Writebol, the two American health care workers flown back for care. While still in Africa, both of them were given an experimental serum developed in the US but never before tried on humans, and it appears to have improved both of their conditions, and likely prevented Dr. Brantly's death. Bringing them back to the US provides their best chance for survival, especially at Emory University Hospital, which has extensive isolation procedures, thanks to its afiliation with the CDC. There is no good reason to leave American citizen health workers in Africa, where hospitals simply lack 1) the ideal treatment and environment for care, and 2) the safeguards and safety equipment to keep the virus from spreading further.
The danger to the United States public is not in patients being brought to the country under controlled conditions, such as Dr. Brantley and Mrs. Writebol. It is in infected persons - who may or may not know they have the virus - traveling here from West Africa and coming in close contact with loved ones once arriving in the US. An infected person may board a plane in West Africa appearing symptom-free, yet arrive home and spread the virus to loved ones through saliva, sweat, or dirty linens even before developing the most worrying symptoms. That said, even if an infected person were to arrive in the United States and mingle among the general population, it is extremely unlikely that there would be a widespread outbreak. First, and it bears repeating, ebola is not spread through casual contact. Second, family units in the United States are less likely than those in Africa to care for ill members at home and prepare their bodies after death, particularly considering recent extensive news coverage of the outbreak. Finally, US hospitals and health care workers are much better prepared and equipped to keep patients in isolation and others away from infectious bodily fluids. Put simply, unless you plan on visiting West Africa, or have close friends or family who have recently visited the area, your chances of acquiring ebola virus disease are negligible. The challenge in controlling this epidemic is convincing many residents of West Africa that temporarily letting go of years of tradition is what is giong to keep them and their families alive.