Why has this Ebola outbreak been so large?

A recurring question about the current Ebola outbreak is how it grew to be so large — and whether the virus has changed modes of transmission or somehow become more infectious.

However, most of the experts at the American Society of Tropical Medicine and Health conference held in New Orleans in early November agreed: The factors leading to increased transmission were more likely to be behavioral.

Dr. Armand Sprecher, MSF

“I think the behavior of the people is different — West Africans have proven to be extraordinarily mobile. During the incubation period they may move from one place to another,” said Dr Armand Sprecher of Médecins Sans Frontières (MSF) during a roundtable on Ebola at the conference. “A colleague has said that, in West Africa, even the dead move. People die in one location, and it may be very important to bury them somewhere else. People take that body and put it on the back of the motorcycle, and somebody will hold on tightly to it. Then, the chauffeur and the person who held the body will both contract the disease. The population have been very mobile and that has caused a significant geographical expansion.”

Dr. Donald Grant of Kenema Government Hospital, Sierra Leone stressed the cultural factors.

“It is the way people show respect for the dead — touching them, and the way people are cared for at home,” he said, and he added, “the borders are imaginary.”

“If you look at anywhere wherever a filovirus outbreak occurs, the social, political and economic background dictates whether it takes off and whether it can be controlled,” Dr. Dan Bausch of Tulane University said.

However, other African health workers at the meeting asserted that such factors were not that much different in Central Africa — surely there was some other reason for the more rapid spread in this context.

But as Bill Gates pointed out in the opening plenary of the conference — part of the difference is that this outbreak has occurred in densely populated urban regions, rather than in simply rural or small village settings where the outbreaks quickly burned out.

Dr. Dan Bausch, Tulane School of Public Health and Tropical Medicine

In addition, Dr. Bausch suggested that there could be indeed something different about Ebola virus disease in this setting — though it is unclear whether it is due to the population affected or viral factors.

“If you look for a biological factor, I think it could be the diarrhea component — the very copious diarrhea 8 to 10 liters a day. My impression and the impression of others is that it is probably more copious in this outbreak — whether that is a viral or a host determinate, this is all speculative. But if you think about it, that could increase the transmission from one person to another. If the person with Ebola is shedding a lot of very infectious stool, it could increase transmission. But that is a biological overlay to the underlying political and social determinants,” he said.


Global Health Strategies generously supported Theo Smart’s attendance at the 63rd Annual American Society of Tropical Medicine and Hygiene Conference in New Orleans.

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