Ebola Epidemic Most Likely Much Larger Than Reported, W.H.O. Says

GENEVA — West Africa’s deadly Ebola epidemic is probably much worse than the world realizes, with health centers on the front lines warning that the actual numbers of deaths and illnesses are significantly higher than the official estimates, the World Health Organization said.

So far, 2,127 cases of the disease and 1,145 deaths have been reported in four nations — Guinea, Liberia, Nigeria and Sierra Leone — the W.H.O announced Friday. But the organization has also warned that the actual number is almost certainly higher, perhaps by a very considerable margin.

“Staff at the outbreak sites see evidence that the numbers of reported cases and deaths vastly underestimate the magnitude of the outbreak,” the group said in a statement on Thursday.

A sick child lies in a classroom used as an Ebola isolation ward in Monrovia, Liberia.

The epidemic is still growing faster than efforts to keep up with it, and it will take months before governments and health workers in the region can get the upper hand, Joanne Liu, the president of Doctors Without Borders, said on Friday, calling conditions on the ground “like a war.”

The situation “is moving faster and deteriorating faster than we can respond,” Dr. Liu told reporters in Geneva after returning a day earlier from a tour of the affected nations.

The epidemic’s front line “is moving, it’s advancing, but we have no clue how it’s going to go around,” Dr. Liu said. “Over the next six months we should get the upper hand on the epidemic,” she added, but this was only a “gut feeling” and it would happen only if sufficient resources were put in place.

Many deaths have occurred within local communities, not at health centers, and the known deaths are “likely the tip of the iceberg,” Dr. Liu said. “We are still having increasing numbers in most of the sites where we work.”

The W.H.O. announced last week that the Ebola epidemic constituted a public health emergency, in a bid to galvanize local and international action. But it has also emphasized that the risk of the epidemic spreading abroad is extremely low.

As countries around the world stepped up precautions for preventing the spread of the disease, the International Olympic Committee announced on Friday that athletes from the countries affected by the Ebola outbreak who are attending the Youth Olympic Games in the Chinese city of Nanjing would not be allowed to compete in contact sports or in the swimming pool.

In addition to this step, which would affect three athletes, it said team members from the affected countries would be subject to regular temperature checks and physical assessments throughout the games.

In its statement on Thursday, the W.H.O. said it was coordinating “a massive scaling up” in support from governments, disease control agencies and other organizations. Margaret Chan, the organization’s director general, met ambassadors in Geneva on Thursday to identify the most urgent needs and seek matching responses, it reported.

Dr. Liu cautioned that “we haven’t turned any corner yet” and that most of the international response was still at the level of promises.

Action to combat the epidemic was at different levels in each of the affected countries, Dr. Liu noted, singling out Liberia as a priority for urgent international attention as it strives to contain the spread of the disease in the capital, Monrovia, a city of 1.3 million people, where one overstretched health care center was providing care for Ebola patients.

“If we don’t stabilize Liberia, we will never stabilize the whole region,” Dr. Liu warned.

The United Nations reported that the World Food Programme was delivering food to more than one million people “locked down” in the quarantine zones where the borders of Guinea, Liberia and Sierra Leone intersect, but Dr. Liu was doubtful about the effectiveness of checkpoints intended to restrict people’s movements.

“I’ve seen it: People are fleeing, people are running around,” she said, describing a checkpoint she had passed where people were walking around it. The local population was not fully supportive and without that, she said, it would be difficult to make the measure effective.