SOURCES: April 15, 2016, Morbidity and Mortality Weekly Report, U.S. Centers for Disease Control and Prevention; April 13, 2016, news conference with Tom Frieden, M.D., MPH, director, U.S. Centers for Disease Control and Prevention; Sonja Rasmussen, M.D., director, division of public health information and dissemination, CDC, and editor-in-chief, Morbidity and Mortality Weekly Report; April 13, 2016, New England Journal of Medicine; April 14, 2016, The New York Times
FRIDAY, April 15, 2016 (HealthDay News) -- Following U.S. health officials' announcement earlier this week that the Zika virus can definitely cause birth defects, many of those same experts are now locked in an unprecedented debate.
Should government health-care officials recommend that American women delay getting pregnant in regions of the country once the mosquito-borne virus becomes active there?
So far, the virus in U.S. territories has been limited to Puerto Rico, the Virgin Islands and American Samoa. But as mosquito season approaches, health experts have said they expect to see infections in Gulf Coast states such as Florida and Texas, as well as Hawaii.
According to The New York Times, some infectious-disease experts believe that avoiding pregnancy during the coming mosquito season is the only way to prevent the birth defect microcephaly, which can lead to abnormally small heads and brains. Most cases of the birth defect have been limited to Brazil, which has reported more than 5,000 suspected or confirmed cases.
But some women's health specialists argue that the government "shouldn't tell women what to do with their bodies," the Times reported. Federal health officials have never suggested that all women in a region of the country avoid pregnancy. Moreover, the specialists say, most babies conceived during Zika epidemics in Latin America -- where the virus has been most prevalent -- have been born healthy, the newspaper said.
For now, the debate continues, with Dr. Tom Frieden, director of the U.S. Centers for Disease Control and Prevention, calling it "a very long conversation."
"We do not have a recommendation to not become pregnant," Frieden said. "We do recommend access to contraception," he added, the Times reported.
Currently, federal health officials recommend that pregnant women avoid areas where Zika is being actively transmitted by mosquitoes. To date, most of the infections have occurred in Latin America and the Caribbean.
The CDC also recommends Zika testing for people potentially exposed to the virus and who have signs or symptoms of infection, typically a fever and rash. For now, that basically means people who have traveled to or lived in Latin America or the Caribbean.
On Friday, the CDC reported that from Jan. 3 to March 5, testing was done on 4,534 persons, including 3,335 (73.6 percent) pregnant women. Among the 1,541 people with one or more Zika-related symptoms, 182 (11.8 percent) had a confirmed Zika infection. Only seven of 2,425 (0.3 percent) symptomless pregnant women were found to be infected.
Reporting in the April 15 issue of their Morbidity and Mortality Weekly Report, CDC officials said that given "the current U.S. setting, where most exposure is travel-associated, the likelihood of Zika virus infection among asymptomatic [symptomless] persons is low." Still, with the risk of microcephaly, "health care providers should continue to offer Zika virus testing to asymptomatic pregnant women with potential exposure."
Health officials also reported this week that gay men can become infected with Zika virus through sexual intercourse. The CDC and Texas health officials detailed the case of a Dallas man who had returned from a trip to Venezuela. He had had sex with his longtime partner, both developed symptoms and both recovered, according to published reports.
In fact, in an estimated 80 percent of cases of Zika infection, the symptoms are mild or the person may not even know they've been infected, according to health officials.
But, Zika also has been linked to Guillain-Barre syndrome, an uncommon nervous system illness in which a person's immune system damages the nerve cells, causing muscle weakness and sometimes paralysis, according to the CDC.
On Wednesday, U.S. health officials announced that the Zika virus is a definite and direct cause of microcephaly and other brain-related birth defects.
"It is now clear," the CDC's Frieden said at a media briefing. "The CDC has concluded that Zika does cause microcephaly."
"There is still a lot that we don't know, but there is no longer any doubt that Zika causes microcephaly," he added.
What's more, it appears that Zika causes a particularly severe form of microcephaly that does terrible damage to infants' brains, Dr. Sonja Rasmussen, director of the CDC's Division of Public Health Information and Dissemination, said at the briefing.
The CDC made its announcement following what it described as a painstaking evidence review led by Rasmussen that was published on an expedited basis on Wednesday in the New England Journal of Medicine, Frieden said.
However, there's still much that needs to be learned about Zika's effect on fetal development, said Rasmussen, who's also editor-in-chief of the Morbidity and Mortality Weekly Report.
For example, no one knows the exact risk of brain-related birth defects to the baby of a mother infected with Zika, she said, because some Zika-infected women have given birth to apparently healthy babies.
"We don't know if the risk is somewhere in the range of 1 percent or in the range of 30 percent," she said. "That's one of the key questions we really want to answer."
Researchers also don't know if Zika will wind up causing learning disabilities to these apparently healthy children later in life, or if Zika also causes birth defects beyond those that are brain-related, Rasmussen added.
The CDC said it hopes that its findings on the Zika-microcephaly connection will prompt pregnant women and women of child-bearing age to be even more careful regarding Zika, Rasmussen said.
Women living in an active Zika region should protect themselves by wearing long-sleeved shirts and long pants, staying indoors with window and door screens to keep mosquitoes out, and using insect repellents.
People also can help cut down on mosquitoes in their neighborhoods by policing their properties and getting rid of any sources of standing water, she said.
"Mosquitoes breed in standing water, especially these mosquitoes," Rasmussen said. "Even small amounts of standing water."
As of April 6, there were 700 confirmed cases of Zika in U.S. states and territories, according to the CDC. However, none of the cases in the continental United States have occurred due to local transmission of the virus via mosquito bite. Nearly all these infections were acquired while traveling outside the country.
Public health officials have said they expect Zika to become active in the United States with the onset of mosquito season. The Aedes aegypti mosquito is expected to be the primary carrier in the United States.
Gulf Coast states are most at risk for local transmission of Zika, CDC officials have said. However, the A. aegypti mosquito ranges as far north as San Francisco, Kansas City and New York City, although health officials have said infections that far north are unlikely.
For more on Zika virus, visit the U.S. Centers for Disease Control and Prevention.
To see the CDC list of sites where Zika virus is active and may pose a threat to pregnant women, click here.