Ryan Van Velzer

The Republic | azcentral.com

An Arizona State University researcher has revealed just how fast Ebola is spreading through West Africa.

Each person infected with Ebola spread the virus to at least one to two other people on average, according to "Early transmission dynamics of Ebola virus disease, West Africa, March to August 2014," a paper published in a European scientific journal Thursday, Sept. 11, written by Gerardo Chowell-Puente, a researcher at Arizona State University's School of Human Evolution and Social Change, and Hiroshi Nishiura, a professor at the University of Tokyo.

The results have signaled a major epidemic with exponential consequences.

If the virus were to continue at the current transmission rate of 1.4 to 1.7 people for each newly person infected, West Africa could gain an additional 77,181 to 277,124 cases by the end of 2014, Chowell-Puente said in an email.

That, however, is the worst-case scenario.

"The above scenario is highly unlikely as the intervention response is definitely improving," he said.

The World Health organization has identified 3,707 cases thus far, including 2,106 confirmed, 1,003, probable and 598 suspected cases among Sierra Leone, Liberia, Nigeria, Guinea and Senegal as of Aug. 31, 2014.

Chowell-Puente and Nishiura conducted a country-specific analysis of transmission rates based on the World Health Organization's total case reports from June to July in Sierra Leone, Guinea and Liberia.

Nishiura said that in order to quell the epidemic, it's necessary to isolate the infected individuals and trace each case back to its source.

"Our findings suggest that control of the Ebola epidemic that has taken so many lives could be attained by preventing more than half of the secondary transmissions for each primary case," Nishiura said.

In essence, if government officials and aid workers can reduce the transmission rate to less than one, the spread of the ebola virus will cease to be an epidemic.

Chowell-Puente said hospitals need to take all possible precautions to prevent the spread of the virus, which is transmitted through contact with bodily fluids. This includes isolating infected individuals, carefully and safely handling the bodies of the deceased—certain rituals involved bathing corpses— and maintaining hand hygiene, he said.

Chowell-Puente and Nishiura note that prior outbreaks have had similar transmission rates before intervention such as the 1995 outbreak in Congo and the 2000 outbreak in Uganda. However, most of the past outbreaks have occurred in isolated rural areas in Central Africa, which were easier to isolate.

"By contrast, this outbreak has been allowed to cross borders from Guinea to neighboring Sierra Leone and Liberia. The virus has reached high density populations. Hence, control requires a much more extensive effort than just placing one single isolation area," Chowell-Puente said, "Every single day that passes with no control could mean additional hundreds of cases when the outbreak is already well advanced."

The researchers note that their analysis is limited by the complex geographical patterns of the region, the ability of the World Health Organization to accurately represent the number of cases and downward bias.

Chowell-Puente is an associate professor at ASU that conducts mathematical and computational modeling with an emphasis on epidemiology and population studies.