Oregon health officials reported on Friday the state’s first case of sexually transmitted Zika infection. The illness was spread from a man who had traveled in a Zika-affected country to his female sex partner, who had not traveled. Both people later tested positive for Zika.

Oregon map Image/ National Atlas of the United States
Oregon map
Image/ National Atlas of the United States

Zika seldom causes serious illness. Four out of five people who get Zika have no symptoms. When symptoms occur, they are generally mild and include fever, rash, joint pain and redness of the eyes.

The disease is concerning, however, because of its potential link to serious birth defects in babies born to women infected during pregnancy.

“Though mosquito bites appear to be the most common way Zika is spread, there is increasing evidence for sexual transmission as well,” says Richard Leman, MD, an OHA public health physician. “People who have been in Zika-affected areas in the previous two weeks and develop symptoms suggesting Zika should see their health care provider. CDC advises men with pregnant sex partners to use condoms or abstain from sex for the duration of pregnancy.”

Related: Oregon reports 1st Zika case of 2016

Zika in pregnant women in the US: Nine cases, 10 others being investigated

The CDC is investigating more than a dozen possible cases of sexual transmission of Zika in the U.S., and has issued interim guidance:

Recommendations for pregnant women and men with pregnant sex partners who live in or have traveled to Zika-affected areas:

  • Pregnant women and their male sex partners should discuss the male partner’s potential exposures and history of Zika-like illness with the pregnant woman’s health care provider. CDC has alist of Zika symptoms on its website. Providers should consult CDC’s guidelines for evaluation and testing of pregnant women, available on the CDC website.
  • Men with a pregnant sex partner who live in or have traveled to an area of active Zika virus transmission should abstain from sex or use condoms during sex (vaginal, anal, or oral) for the duration of the pregnancy. Using latex condoms every time reduces the risk of sexual transmission of many infections, including those caused by other viruses.
  • Pregnant women should consider postponing travel to Zika-affected regions. If they choose to go, they should take steps to avoid any contact with mosquitoes.

Recommendations for non-pregnant women, and men with non-pregnant sex partners who live in or have traveled to Zika-affected areas:

  • It is still unclear whether Zika infection during pregnancy is responsible for recently reported birth defects involving brain development. Public health investigators are continuing their efforts to answer this question. In Oregon, public health officials are following these investigations closely and will continue to update their guidance to the public as they learn more.
  • In the meantime, couples in which a man has recently spent time in an area with Zika virus transmission might wish to weigh this potential risk in their decisions about whether to use condoms during sexual activity.

Zika also may increase the risk of Guillan-Barré Syndrome, a problem marked by muscle weakness and sometimes paralysis. Public health investigators are working hard to determine whether Zika actually causes this condition.