U.S. Scientists See Long Fight Against Ebola

The deadly Ebola outbreak sweeping across three countries in West Africa is likely to last 12 to 18 months more, much longer than anticipated, and could infect hundreds of thousands of people before it is brought under control, say scientists mapping its spread for the federal government.

“We hope we’re wrong,” said Bryan Lewis, an epidemiologist at the Virginia Bioinformatics Institute at Virginia Tech.

Both the time the model says it will take to control the epidemic and the number of cases it forecasts far exceed estimates by the World Health Organization, which said last month that it hoped to control the outbreak within nine months and predicted 20,000 total cases by that time. The organization is sticking by its estimates, a W.H.O. spokesman said Friday.

Relatives of a man who died of what appeared to be Ebola waited outside their home in Monrovia while a team of workers sprayed and disinfected the area.Cuts at W.H.O. Hurt Response to Ebola CrisisSEPT. 3, 2014
graphic What You Need to Know About the Ebola OutbreakJULY 31, 2014
But researchers at various universities say that at the virus’s present rate of growth, there could easily be close to 20,000 cases in one month, not in nine. Some of the United States’ leading epidemiologists, with long experience in tracking diseases such as influenza, have been creating computer models of the Ebola epidemic at the request of the National Institutes of Health and the Defense Department.

Dr. Margaret Chan, director general of the W.H.O., which has stood by its lower projections of the toll of the Ebola outbreak. Credit Martial Trezzini/KEYSTONE, via Associated Press
The Centers for Disease Control and Prevention declined to comment on the projections. A spokesman, Tom Skinner, said the agency was doing its own modeling and hoped to publish the results soon. But the C.D.C. director, Dr. Thomas R. Frieden, has warned repeatedly that the epidemic is worsening, and on Sept. 2 described it as “spiraling out of control.”

While previous outbreaks have been largely confined to rural areas, the current epidemic, the largest ever, has reached densely populated, impoverished cities — including Monrovia, the capital of Liberia — gravely complicating efforts to control the spread of the disease. Alessandro Vespignani, a professor of computational sciences at Northeastern University who has been involved in the computer modeling of Ebola’s spread, said that if the case count reaches hundreds of thousands, “there will be little we can do.”

What worries public health officials most is that the epidemic has begun to grow exponentially in Liberia. In the most recent week reported, Liberia had nearly 400 new cases, almost double the number reported the week before. Another grave concern, the W.H.O. said, is “evidence of substantial underreporting of cases and deaths.” The organization reported on Friday that the number of Ebola cases as of Sept. 7 was 4,366, including 2,218 deaths.

“There has been no indication of any downturn in the epidemic in the three countries that have widespread and intense transmission,” it said, referring to Guinea, Liberia and Sierra Leone.

The scientists who produced the models cautioned that their dire predictions were based on the virus’s current uncontrolled spread and said the picture could improve if public health efforts started to work. Because conditions could change, for better or for worse, the researchers also warned that their forecasts became shakier the farther into the future they went.

Dr. Lewis, the Virginia Tech epidemiologist, said that a group of scientists collaborating on Ebola modeling as part of an N.I.H.-sponsored project called Midas, short for Models of Infectious Disease Agent Study, had come to a consensus on the projected 12- to 18-month duration and very high case count.

Another Midas participant, Jeffrey L. Shaman, an associate professor of environmental health sciences at the Columbia University Mailman School of Public Health, agreed.

“Ebola has a simple trajectory because it’s growing exponentially,” Dr. Shaman said.

Lone Simonsen, a research professor of global health at George Washington University who was not involved in the modeling, said the W.H.O. estimates seemed conservative and the higher projections more reasonable.

“The final death toll may be far higher than any of those estimates unless an effective vaccine or therapy becomes available on a large scale or many more hospital beds are supplied,” she said in an email.
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