Nav: Home

Sexual transmission of Ebola likely to impact course of outbreaks

June 07, 2016

Athens, Ga. - 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 University of Georgia ecologists just published in the Royal Society journal Biology Letters.

The potential for sexual transmission is high for three to four months after the virus has been cleared from the bloodstream, and possible for an average of seven months.

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 College of Veterinary Medicine's department of infectious diseases. "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.

First, they created a model population of 1,000 individuals and introduced 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.

"An important point to make is that without the behavior changes and interventions, it would have been more like 80 percent of individuals infected," said Park. "The actions taken in West Africa were very effective."

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 student in the Odum School.

There were, however, two components of sexual transmission about which very little is known. The first is what proportion of people who survive Ebola are actually able to transmit the virus through sexual contact; the second is how the rate of sexual transmission compares to that of regular transmission.

To overcome this lack of data, they ran the model using values that varied widely for both questions but within plausible limits.

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.

The model shows that even the smallest and shortest outbreaks in the presence of sexual transmission were larger and longer-lasting than outbreaks where no sexual transmission occurred.

"Whenever we had die-outs of the directly transmitted infectious individuals, which would otherwise have spelled the end of the outbreak, we had reignition from the sexually infectious individuals transmitting the virus to the susceptible people left in the population, who then served as a source of direct transmission," Vinson said. "Thinking about it from the parasite's point of view, the parasite is able to persist in that population even without the direct contact transmission by symptomatic individuals."

Park said the findings point to the importance of considering alternative pathways of disease transmission.

"There's an increasing awareness that sexual transmission can happen in addition to a more clearly evidenced transmission route and not just with Ebola," he said. "But there's been very little written about how it works or what it means for the metrics that the public health community uses. Our model is ultimately translatable to other disease systems and shows how it can be done even under uncertainty of key parameters."
-end-
The study, "The potential for sexual transmission to compromise control of Ebola virus outbreaks," is available online at http://dx.doi.org/10.1098/rsbl.2015.1079.

Co-authors are John Drake, an associate professor in the Odum School, and Pejman Rohani, a professor in the Odum School and College of Veterinary Medicine. Support for the research was provided by the National Institute of General Medical Sciences of the National Institutes of Health under award number U01GM110744 and by the National Science Foundation.

University of Georgia

Related Ebola Articles:

Ebola antibodies at work
Scientists in Israel and Germany show, on the molecular level, how an experimental vaccine offers long-term protection against the disease.
Half of Ebola outbreaks undetected
An estimated half of Ebola virus disease outbreaks have gone undetected since it was discovered in 1976, according to research published in PLOS Neglected Tropical Diseases.
Half of Ebola outbreaks go undetected, study finds
Half of Ebola outbreaks have gone undetected since the virus was discovered in 1976, scientists at the University of Cambridge estimate.
Protecting those on the frontline from Ebola
Online training developed at the Medical University of South Carolina (MUSC) increased the knowledge of health care workers about effective prevention of Ebola up to 19 percent and reduced critical errors to 2.3 percent in a small MUSC cohort.
Another piece of Ebola virus puzzle identified
A team of researchers have discovered the interaction between an Ebola virus protein and a protein in human cells that may be an important key to unlocking the pathway of replication of the killer disease in human hosts.
How the human immune system protects against Ebola
'The current approach for treatment of filovirus infections with antibody cocktails tested in animal models utilizes the principle of targeting of non-overlapping epitopes.
How to slow down Ebola
The phylogenetic tree of the 2013-2016 Ebola epidemic doesn't just tell us how the Ebola virus was able to evolve: it also reveals which events and preventive measures accelerated or slowed down its spread.
Study provides further insight into how Ebola affects the eye
A new study, conducted by the researchers from the University of Liverpool, published in JAMA Ophthalmology identifies the specific characteristics of Ebola retinal lesions, which provide further clues as to how the virus travels to the retina and causes damage.
New breakthrough paving the way for universal Ebola therapeutic
A new collaborative study has identified and studied Ebola antibodies that could be used to design universal therapeutics that are effective against many different Ebola species.
Preprints accelerated between Ebola and Zika epidemics
Preprints -- scientific manuscripts that are posted at a recognized online repository before peer review -- have the potential to speed up the reporting of scientific research in infectious disease outbreaks, argue Michael Johansson and colleagues in an Essay in PLOS Medicine.
More Ebola News and Ebola Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#541 Wayfinding
These days when we want to know where we are or how to get where we want to go, most of us will pull out a smart phone with a built-in GPS and map app. Some of us old timers might still use an old school paper map from time to time. But we didn't always used to lean so heavily on maps and technology, and in some remote places of the world some people still navigate and wayfind their way without the aid of these tools... and in some cases do better without them. This week, host Rachelle Saunders...
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.