University Of Miami Researcher Models Sexual Transmission Of Zika

Jul 6, 2016

There will be 450,000 condoms distributed at the 2016 Olympics, three times more than the number distributed during the 2012 Olympics.

Safe sex is  a special priority this year in Brazil. The host of the 2016 Olympics has reported more than 100,000 cases of Zika virus and the virus can be transmitted by men to their sexual partners. That makes it different from other mosquito-borne illnesses like Dengue Fever and Chikungunya.

Shigui Ruan, one of six researchers who made a mathematical model of the spread of zika.
Credit University of Miami

A team of researchers, including a University of Miami mathematician, recently modeled the contribution of sexual transmission to the spread of the virus. In a study published last month, they estimated that about  3 percent of new Zika cases in Brazil, El Salvador and Colombia can be attributed to sexual transmission.

There is heightened interest around sexual transmission of Zika after recent reports suggesting it plays a greater role in transmission than previously thought. One study found that in the city of Rio de Janeiro, Brazil, there are 90 percent more Zika cases among women of age to be sexually active than in men of their ages. In outbreaks of dengue fever, which is not spread sexually, women were only 30 percent more likely to report cases of the disease.

In an interview last week, Shigui Ruan, a professor of mathematics at the University of Miami, said that he took an interest  in sexual transmission of Zika largely because sexual transmission sets it apart from other diseases spread by mosquitoes.

“This is the first kind of vector-borne disease that can be transmitted sexually,” Ruan said. “That’s why we were so curious about it.”

He said that sexual transmission can make an outbreak last longer.

“The virus stays in the semen much longer than in the blood, which makes the disease much more complicated and more difficult to prevent,” he said.

Ruan, who is from Central China, conducted the study along with researchers from other universities in the U.S. and China.

The mathematical model found that each person infected with zika can infect about two other people. That number is based on environmental conditions in the countries that they studied, like rates of mosquito bites and unprotected sex.

The researchers found also that “sexual transmission alone is unlikely to initiate or sustain an outbreak,” but that it should not be ignored.

Ruan said in countries with very high rates of Zika like Brazil, a three percent rate means a high number of individuals infected with Zika by sexual transmission.

The CDC doesn’t know now whether men infected with Zika who don’t have symptoms can pass the virus to sex partners, and Ruan’s study assumed they cannot.

Florida saw its first case of Zika-related birth defects last week. Because of the risk of birth defects that the virus poses the CDC is recommending now that men who live in or travel to areas with Zika who have partners that are pregnant use condoms or don’t have sex.

Ruan is currently researching the potential for the spread of Zika by mosquitoes in Miami.