Ebola could spread faster than projected, US scientists warn

Ebola could spread faster than projected, US scientists warn

Saturday, September 13, 2014 10:01 am


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, The New York Times reported today, quoting a report by American scientists given to the US 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 Organisation, which said last month that it hoped to control the outbreak within nine months and predicted 20,000 total cases by that time. The organisation is sticking by its estimates, a W.H.O. spokesman said Friday.

A woman passes by a man knocked down by Ebola in Monrovia

A woman passes by a man knocked down by Ebola in Monrovia

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 Defence Department.

The Centers for Disease Control and Prevention declined to comment on the projections. A spokesman, Tom Skinner, said the agency was doing its own modelling 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 “spiralling 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 modelling 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 organisation 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.

Assuming current infection rates continue, a new model estimates there could be 20,000 Ebola cases by mid-October. The model’s estimate would nearly triple under deteriorating conditions and an increasing infection rate.

Dr. Lewis, the Virginia Tech epidemiologist, said that a group of scientists collaborating on Ebola modelling 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.
.Reported by New York Times


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