The Ebola epidemic in West Africa is growing exponentially, says a new study published in the journal PLoS Outbreaks that suggests if new control measures are not enacted, new cases could reach 6,800 by the end of September.
Using World Health Organization (WHO) data up to 8 September 2014, the study team – from Arizona State University (ASU) and Harvard School of Public Health – analyzed local rates of exponential rise to estimate how the reproduction number of Ebola cases appears to be changing over time.
The reproduction number of a disease is the average number of secondary cases that a case generates. When control measures are effective – and the virus does not change into a more infectious one – one expects this number to go down.
The study’s statistical models predict an average of 4,400 – with an upper figure of 6,800 – new cases by the end of this month, indicating that the pace of Ebola spread is accelerating.
Using statistical models, the researchers found at the time that Liberia and Guinea implemented mass quarantine in August, the reproduction number of Ebola cases rose significantly rather than fell, suggesting mass quarantine was not a good idea, as first author Sherry Towers, a research professor at ASU, explains:
“There may be other reasons for the worsening of the outbreak spread, including the possibility that the virus has become more transmissible, but it’s also possible that the quarantine control efforts actually made the outbreak spread more quickly by crowding people together in unsanitary conditions.”
When the mass quarantine was implemented, they sparked riots in the quarantine areas as living conditions and sanitation deteriorated.
This is the first time West Africa has experienced an outbreak of Ebola. The outbreak there is unusual in that the disease has not only spread over a large geographical area, but it has also spread to densely populated regions, which raises the risk of spreading internationally.
The authors note the problem is made worse because of a widespread shortage of resources for effective quarantine and isolation, and because of a highly mobile population and porous borders in the three countries affected – Guinea, Liberia and Sierra Leone.
Co-author Carlos Castillo-Chavez, Regents Professor at ASU, explains since there is no licensed vaccine or specific treatment for Ebola virus disease, the only way to control the epidemic is via improved hygiene, quarantine, isolation and social distancing: “Improved control measures must be put into place,” he urges.
In a recent impassioned speech to the United Nations, the Doctors Without Borders (MSF) International President, Dr. Joanne Liu, said the ground response to the Ebola epidemic “remains totally and lethally inadequate.”
She said “transmission rates are at unprecedented levels,” and with every passing week the epidemic “grows exponentially,” and the response becomes all the more complicated.
She urges, “More countries must deploy their civil defence and military assets, and medical teams, to contain the epidemic.”
On 16 September, President Obama announced the US was sending 3,000 troops and medical personnel to West Africa to help control the epidemic.
Funds from the National Institute of General Medical Sciences at the National Institutes of Health helped finance the study.
Meanwhile, WHO announced earlier this month that lab tests show a new outbreak of Ebola in the Democratic Republic of Congo is a “distinct and independent event” and not derived from strains circulating in the current West African epidemic.