Containing an outbreak by a lethal pathogen places big demands on workers in any health system, but this is especially the case in one of the world's poorest regions, they say.
Peter Piot, director of the London School of Hygiene and Tropical Medicine, who co-discovered the Ebola virus in 1976, said health workers faced "their own fear of this epidemic, a fear that is grounded in reality. They're the front line."
"They often don't have the resources, they see colleagues dying, so I'm not surprised that some hospitals have been abandoned, basically," he said in an interview with AFP in London.
"Some nurses in some hospitals have gone on strike because there isn't a minimum basic equipment for protecting both the hospital workers and the patients and their relatives."
"The health workers are tired," said Jean-Claude Manuguerra, a professor at the Pasteur Institute in Paris who spent two weeks at the Donka Hospital in Conakry, the capital of Guinea, the country that has been at the epicentre of the scare.
"It's hard to recruit people and get them to come. Some aren't available, and there's the factors of fatigue and fear."
The epidemic has caused more than 670 deaths and 1,200 cases in Guinea, Liberia and Sierra Leona, with one case confirmed in Nigeria.
Piot on Wednesday said the number of cases in Guinea appeared to be in decline but was rising in Liberia and Sierra Leone, where it had become "a national emergency" in the two countries.
Brigitte Vasset, deputy medical director at the French-based charity Medecins Sans Frontieres (MSF), or Doctors without Borders, said tackling an Ebola outbreak required a large pool of personnel.
They were not just doctors and nurses who had to handle infected patients, she said.
Around half are people who take care of things such as logistics and cleaning and going to homes to trace relatives or friends of people who have fallen sick.
They, too, need to be trained in infection risk, she said in a phone interview.
Every extension of the outbreak ratchets up the demand for resources, she said.
Foreign staff for MSF who were being sent to fight the epidemic are being rotated every three weeks "before they go beyond the point of exhaustion," she said.
"We can no longer respond to every outbreak," Vasset warned. "We just don't have the staff to train other people properly and ensure that they are not placed at risk. We need to have more people, more specialists."
- '40 minutes, maximum' -
The Ebola virus is transmitted through contact with the blood, body fluids, secretions or organs of an infected person.
After an incubation period of up to 21 days, the virus causes severe fever and muscle pain, weakness, vomiting and diarrhoea, and in some causes unstoppable bleeding that shuts down vital organs.
Treating patients with Ebola means donning a full protective suit, mask, gloves and goggles, which according to medical guidelines is then checked by a fellow worker to ensure there are no gaps to expose the skin.
The outfit is being worn in searing tropical heat, in clinics where there is no air conditioning, Vasset said. "You can stand it for 40 minutes maximum, then have to be replaced."
Those who go to remote villages to try to trace people who have been in contact with patients, or to educate locals about the risks of contamination, may encounter hostility from inhabitants who suspect they are bringing the virus, said Mariano Lugli, coordinator of MSF's operations in Guinea.
"We are being threatened if we go to certain villages," he told AFP on Monday. "There are regions where we don't have access and have absolutely no idea what's going on there."