Sexual transmission of the Ebola virus could have a major impact on the dynamics of the disease, potentially reigniting an outbreak that has been contained by public health interventions, according to research by UGA ecologists published in the Royal Society journal Biology Letters.
The research was prompted by the publication of data showing that viable Ebola virus remained in the semen of disease survivors for months after it was no longer detectable in their blood—and by a study reporting at least one instance of sexual transmission of Ebola.
“We realized that this could be a hidden source of the virus,” said senior author Andrew Park, an associate professor in the UGA Odum School of Ecology and the College of Veterinary Medicine’s infectious diseases department. “We wanted to find out what role sexual transmission might play in the dynamics of an outbreak.”
The researchers developed a mathematical model to test various outbreak scenarios.
They created a model population of 1,000 individuals and introduced the Ebola virus to track its spread via regular transmission. Based on the experience of the 2014 outbreak, they assumed that many actions would be taken, from individual behavior changes to public health interventions, to control the outbreak. In the parameterized model, this resulted in one in four individuals infected throughout the population.
Next, they set out to determine the impact that sexual transmission could have.
“We wanted to know what it would mean in terms of the size of an outbreak, how long an outbreak lasts, how likely an outbreak is to occur and the reproductive ratio of the parasite, a measure of how effectively the parasite transmits in populations,” said the study’s lead author, John Vinson, a doctoral candidate in the Odum School.
Their results showed a clear impact from sexual transmission. When the values of both parameters—the number of sexually infectious individuals and the rate of transmission—were low, outbreaks were smaller and ended more quickly, but as the values increased, so did the size and duration of outbreaks.
Co-authors are John Drake, an associate professor in the Odum School, and Pejman Rohani, a professor in the Odum School and the College of Veterinary Medicine.