Yet another set of ominous projections about the Ebola epidemic in West Africa was released Tuesday, in a report from the Centers for Disease Control and Prevention that gave worst- and best-case estimates for Liberia and Sierra Leone based on computer modeling.
In the worst-case scenario, Liberia and Sierra Leone could have 21,000 cases of Ebola by Sept. 30 and 1.4 million cases by Jan. 20 if the disease keeps spreading without effective methods to contain it. These figures take into account the fact that many cases go undetected, and estimate that there are actually 2.5 times as many as reported.
The report does not include figures for Guinea because case counts there have gone up and down in ways that cannot be reliably modeled.
In the best-case model — which assumes that the dead are buried safely and that 70 percent of patients are treated in settings that reduce the risk of transmission — the epidemic in both countries would be “almost ended” by Jan. 20, the report said. It showed the proportion of patients now in such settings as about 18 percent in Liberia and 40 percent in Sierra Leone.
“My gut feeling is, the actions we’re taking now are going to make that worst-case scenario not come to pass,” Dr. Thomas R. Frieden, the C.D.C. director, said in a telephone interview. “But it’s important to understand that it could happen.”
The figures in the C.D.C. report are based on data from August, but Dr. Frieden said the situation appeared to have improved since then because more aid had begun to reach the region.
The current official case count is 5,843, including 2,803 deaths, according to the World Health Organization.
The W.H.O. published its own revised estimates of the outbreak on Monday, predicting more than 20,000 cases by Nov. 2 if control does not improve. That figure is more conservative than the one from the C.D.C., but the W.H.O. report noted that many cases were unreported and said that without effective help, the three most affected countries would soon be reporting thousands of cases and deaths per week. It said its projections were similar to those from the C.D.C.
The W.H.O. report also, for the first time, raised the possibility that the disease would not be stopped but would become endemic in West Africa, meaning that it could become a constant presence there. The report from the C.D.C. did not discuss that possibility, but it is something that health officials have feared all along, and the reason they say help is needed so quickly.
President Obama’s promise last week to send 3,000 military personnel to Liberia and to build 17 hospitals there, each with 100 beds, were part of the solution, Dr. Frieden said. He said the Defense Department had already delivered parts of a 25-bed unit that will soon be set up to treat health workers who become infected, a safety measure he said was important to help encourage health professionals to volunteer. He added that aid groups were flooding into the region and setting up treatment centers.
The W.H.O. reported on Wednesday that a new treatment center had just opened in Monrovia, the Liberian capital, with 120 beds for treatment and 30 for triage. Patients were already lined up at the door.
The report from the C.D.C. acknowledged that case counts were rising faster than hospital beds could be provided. It said that in the meantime, different types of treatment would be used, based in homes or community centers, with relatives and others being given protective gear to help keep the disease from spreading.
The United States government is also sending 400,000 kits containing gloves and disinfectant to Liberia to help families take care of patients at home. The kits reflect the recognition that even the most ambitious new program will not be able to add hospital beds fast enough to keep up with the disease.
At least one aid group working in Liberia is already shifting its focus to teaching people about home care and providing materials to help. Ken Isaacs, a vice president of the aid group Samaritan’s Purse, said, “I believe inevitably this is going to move into people’s houses, and the notion of home-based care has to play a more prominent role.” He said there could be 100,000 or more cases by the end of 2014.
“Where are they going to go?” Mr. Isaacs asked. “It’s too late. Nobody’s going to build 100,000 beds.”
Though providing home-care kits may seem like a pragmatic approach, some public health authorities said they were no substitute for beds in isolation or containment wards.
But Dr. Frieden said that home care had been used to help stamp out smallpox in Africa during the 1960s. The caregivers were often people who had survived smallpox themselves and were immune to it. Some experts have suggested that Ebola survivors might also be employed to care for the sick.