Ebola outbreaks are simultaneous ’mini-epidemics’

Different viral strains responding to ideal conditions

Though they may appear as single outbreaks quickly spread by people and wildlife, recent flare-ups of the deadly Ebola virus in Central Africa are actually multiple epidemics of different viral strains, simultaneously appearing when conditions are ideal, according to a study appearing in the journal Science.

The study, authored by the New York-based Wildlife Conservation Society and other groups, said that scientists previously believed that the virus forms in epicenters and quickly spreads by animals moving through the forest. Eventually people catch the disease by handling or eating infected wildlife. Ebola causes hemorrhagic fever and death within a few days for most of its victims.

“Now we know that the virus doesn’t ’spread’ as much as it spills over from many sources in the forest,” said Dr. William Karesh head of WCS’s Field Veterinarian Program and co-author of the study. “This study changes the way Ebola outbreak-response teams will look at the disease and minimize its damage to both people and wildlife.”

The authors discovered that an outbreak between October 2001 and May 2003 actually consisted of eight viral strains originating from different areas. What causes simultaneous flare-ups is still unknown, as are the natural hosts that spread the disease.

The authors also said that most infections among humans continue to occur after a dead or dying animal is found by a local person, noting that large numbers of animal carcasses are sometimes seen in forests just prior to humans coming down with the disease. They recommend that a monitoring network to look for dead and dying large animals be established as an early warning system.

Gorillas in particular, have been hard-hit by the Ebola, the authors said, pointing out that mortality by diseases, coupled with rampant poaching and habitat loss, may lead to their extinction in western Central Africa.