The Centers for Disease Control and Prevention announced today that men who travel to Zika-affected regions should practice abstinence or safe sex with condoms with pregnant partners for the entirety of a woman’s pregnancy.
The announcement followed this outbreak’s first case of sexually transmitted Zika, which was reported in Dallas on Tuesday. Another report today from Brazil suggests the virus can also be found in saliva and urine. However, the CDC’s new guidelines on sexual transmission don’t include advice on whether partners should avoid kissing, given that more research is needed to determine whether the disease can be transmitted via saliva.
“I understand that this is a stressful situation for women and families. I wish we knew more about Zika today. I wish we could do more about Zika today,” CDC director Tom Frieden said in a press conference. “We’re committed to finding out what we can, as fast as we can.”
Frieden’s remarks ushered in two sets of guidelines on the Zika virus, which has been blamed for a swell of microcephaly cases — a fetal development disorder — in Brazil. The virus has also been speculatively tied to Guillain-Barre disease, which can cause paralysis in adults.
“With each passing day, the linkage between Zika and microcephaly becomes stronger. In addition, the linkage between Zika and Guillain-Barre syndrome also appears stronger,” Frieden said.
The first set of guidelines deal with sexual transmission and recommend that pregnant women practice abstinence or safe sex with condoms with male partners who reside in or have traveled from Zika-stricken areas. As of now, this advice applies for the entire duration of pregnancy.
That’s because of a current gap in the understanding of when a developing fetus is most at-risk for Zika-related microcephaly. The Pan American Health Organization has stated the greatest risk of microcephaly and malformations appears to be associated with infection during the first trimester of pregnancy. Frieden echoed this point.
“If Zika behaves as many other infectious and toxic causes of fetal malformations, then the first trimester and the early part of the second trimester would be the highest risk time,” Frieden said.
However, he continued, if researchers ultimately learn that the virus is “neurotropic” — that it targets brain tissue — then the disease could be a threat to any stage of pregnancy. That’s why the CDC advises that women in any stage of pregnancy should not travel to areas where Zika is spreading, should use mosquito-fighting techniques to lower their risk of infection and should avoid unprotected sex with men exposed to the virus, he said.
“We know that semen may have large quantities of viable virus for at least a short period of time after Zika virus infection. We will be doing studies of how long the virus can persist in semen, but we know it goes away from the blood within about a week,” Frieden said. Though the CDC is investigating oral, anal and vaginal sex as modes of Zika virus transmission, their risk assessment only applies to sex between pregnant women and sex with a potentially infected male.
Despite the connection to sexual transmission, Frieden emphasized that mosquitoes are still the primary route for catching Zika virus and warned about the aggressiveness of the primary carrier in the tropics: the Aedes aegypti mosquito.
“It bites four to five people with every meal, it has a relatively painless bite so you don’t swat and kill it, and it can breed in as much as a drop of water in a bottle cap,” Frieden said. He added that anytime there are lots of cases of a condition, you will see rare cases of a virus getting transmitted via sexual transmission of a virus without a prior history of doing so. So far, sexual transmission of the virus from infected women to their partners has not been reported.
The findings on saliva and urine, even with the report from Brazil, are less clear, Frieden said. When asked whether couples impacted by Zika virus should refrain from kissing, he said more evidence is required before the CDC can issue guidance.
“The fact that the infectious particles are found in the saliva does not mean that a person can become infected by ingesting saliva,” University of Pittsburgh microbiologist Ernesto T.A. Marques said in an email to PBS NewsHour.
For saliva to transmit Zika, the virus would need to cross the internal skin lining of the throat or the gut, in order to gain access to a person’s blood, and “so far we do not have any data that indicate that is possible,” Marques said.
Blood transfusions, however, are a rare but possible route for spreading the disease. The AABB, formerly known as the American Association of Blood Banks, said on Tuesday that it would deny prospective donors who have visited Zika-affected areas in the last 28 days.
The CDC’s second set of guidelines update their advice for health care providers, given new improvements in serological tests for the Zika virus. These tests look for IgM antibodies that are produced by the human body to fight the microbe and, in theory, they could be administered several weeks after the virus has been cleared from the blood.
So far, genetic testing has been the best method for spotting the virus, while ultrasounds serve as a means for catching the signs of microcephaly in a developing fetus.
“We’ve heard from the provider community that serial ultrasounds were very challenging….and we’re rolling out the availability of serological testing,” Frieden said. The CDC is aiming to increase production of these tests and deliver them to health care providers who have complained of having limited means to diagnose Zika in pregnant women. “Not everyone who wants a test can get it, we’re working as fast as we can to increase the availability of testing.”