An "unprecedented" number of doctors and nurses have been infected with Ebola virus in west Africa, according to the World Health Organization.
More than 2,600 people in Guinea, Liberia, Nigeria and Sierra Leone have been infected since March, including more than 240 health care workers.
Infections in medical workers are due to a shortage of protective equipment and staff, said the health body.
Only one or two doctors are available for 100,000 patients in some countries.
The WHO said the "heavy toll on health care workers" had consequences that further impeded control efforts, such as the closure of health facilities.
"Ebola has taken the lives of prominent doctors in Sierra Leona and Liberia, depriving these countries not only of experienced and dedicated medical care but also of inspiring national heroes," the WHO said in a statement.
"In many cases, medical staff are at risk because no protective equipment is available - not even gloves and face masks."
The current outbreak is the largest ever, and has killed an estimated 2,615 people.
About half of those infected have died.
A US health official visiting the three hardest hit countries - Liberia, Sierra Leone and Guinea - said the virus had the `"upper hand'' in the outbreak, but experts had the tools to stop it.
"Lots of hard work is happening, lots of good things are happening,'' said Dr Tom Frieden, the director of the US Centers for Disease Control and Prevention. "But the virus still has the upper hand.''
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