Study suggests Zika virus won’t be passed on through saliva

Recently published research from UW-Madison suggests the Zika virus is unlikely to be passed through saliva.

This study, published Tuesday in the Nature Communications journal, sheds more light on a virus that has captured the attention of the national media as well as that of the worldwide medical community.

It’s been linked to birth defects like microcephaly, a condition where the baby’s head is smaller than expected, and can be passed from a pregnant mother to a fetus, according to the Centers for Disease Control and Prevention.

Scientists say the Zika virus can be transmitted through mosquito bite, but evidence also exists for the transmission of Zika through intercourse. Once infected, a person’s saliva and blood contain the virus for about two weeks, but it stays longer in bodily fluids like breast milk and semen.

The study says the Zika virus is not likely to be passed by kissing or other casual contact like sharing silverware or trying someone’s drink.

“If passing the virus by casual contact were easy, I think we would see a lot more of what we would call secondary transmission in a place like the United States,” says Tom Friedrich, a virology professor at the UW-Madison School of Veterinary Medicine.

He says scientists and public health officials aren’t seeing ‘clinically apparent’ spread of the virus without the presence of mosquitoes that carry the virus.

To obtain these study results, researchers at the Wisconsin National Primate Research Center infected rhesus macaque monkeys with a strain of Zika virus, then collected their saliva. The scientists then administered that infected saliva to the tonsils of five uninfected monkeys, and also swabbed the tonsils of three other monkeys with a concentrated high dose of the virus.

None of the monkeys dosed with infected saliva developed the infection, but all three exposed to the more concentrated virus were infected with Zika.

“Our study helps to put into context some of the transmission risk,” Friedrich said.

In mid-July, the Wisconsin Department of Health Services reported that a mosquito with the capacity to carry Zika — Aedes albopictus — was discovered in Dane County.

All in all, eggs from this type of mosquito were found at four separate occasions this summer — two in Dane County, and two in Waukesha County, according to Susan Paskewitz, professor and department chair in the department of entomology at UW-Madison.

She says these mosquitoes, which thrive in warmer climates, have probably been around Wisconsin for quite some time in small pockets, and they have also been found in Illinois and Minnesota.

But Wisconsinites shouldn’t be unduly troubled by these discoveries, Paskewitz told, because the harsh winters keep the heat-loving insect from flourishing.

“I think they will fail to establish,” she said, adding that any populations in the state aren’t likely to grow much, or even expand out of the localized areas where they’ve been found.

“The detection of the Aedes albopictus mosquito in Wisconsin is not a cause for alarm,” added Karen McKeown, a state health officer for DHS. “We can look to nearby states that also have small numbers of these mosquitoes, where Zika virus has not been locally spread.”

According to the state Department of Health Services, all Zika virus cases in Wisconsin so far have been travel-related.

–By Alex Moe