The virus is best known for its links to a devastating fetal birth defect known as microcephaly, where babies are born with smaller-than-expected heads and brains. But Zika's links to miscarriage haven't been clear.
"Data linking Zika virus infection to fetal death have been reported in only a handful of cases," wrote a team led by Dr. Annemiek van der Eijk, of Erasmus Medical Center in Rotterdam, the Netherlands.
First trimester loss
The researchers said a 31-year-old Dutch woman lost her baby at 11 weeks' gestation, after contracting Zika on a trip to the South American country of Suriname. Suriname borders Brazil, which has been hit hard by thousands of cases of Zika-linked microcephaly.
The report was published online July 27 in the New England Journal of Medicine. In it, the researchers described how the pregnant woman became ill with headache, joint pain and rash the day after she returned to the Netherlands after more than three weeks in Suriname.
She recovered after six days. But, about two weeks after her symptoms first emerged, doctors found no fetal heartbeat -- indicating a miscarriage -- when the woman went in for a routine ultrasound. She received a D&C (dilation and curettage) a week later.
Traces of Zika virus were found in amniotic fluid, placental tissue, and in the mother's urine and blood, van der Eijk's team noted. The virus was also found in fetal stem cells, suggesting that Zika "replicates in [these cells] involved in early stage embryo development," the researchers explained.
The study can't prove that maternal Zika infection caused the miscarriage, only that there was an association. However, the Dutch team pointed out that traces of Zika virus in blood and fetal tissue were found for at least 21 days, suggesting that the "window" for testing a pregnant woman for the virus may need to be expanded. The current testing window set by the U.S. Centers for Disease Control and Prevention is 14 days.
CDC revised Zika advice
In the United States, the CDC has been keeping a close eye on Zika, and revising its recommendation for pregnant women accordingly.
On Monday, the CDC updated its guidelines to say that pregnant women could contract Zika from a sex partner of either gender. While mosquitoes remain the biggest source of infection, cases of sexually transmitted Zika do occur.
Based on that, the CDC now "recommends that all pregnant women with sex partners (male or female), who live in or traveled to an area with Zika, use condoms during sex or abstain from sex for the remainder of their pregnancy," the agency said.
"Sex includes vaginal, anal and oral sex, and may also include the sharing of sex toys," the CDC said.
Any pregnant woman who suspects that she may have been exposed to Zika -- either through a mosquito bite or sexual contact with an infected person -- should be tested for the virus, the agency stressed.
The CDC also pointed out that "new information has indicated that some infected pregnant women can have evidence of Zika virus in their blood for longer than the previously recommended seven-day window."
Because of that new data, the agency updated its recommendation to lengthen the time frame for blood testing for Zika to 14 days.
The vast majority of cases of Zika-linked illness and birth defects are occurring in Latin America. However, Zika may be making inroads into the United States. Florida health officials said they are investigating several possible cases of locally transmitted Zika infection.
The first possible case of local infection in the continental United States was reported last week by the Florida health department. That case involved a woman in Miami-Dade County. Additional cases are also now being investigated there and in Broward County, north of Miami.
Florida health officials said they were capturing and testing mosquitoes in the neighborhoods involved. Meanwhile, Gov. Rick Scott has asked for assistance from the CDC, The Miami Herald reported.
The CDC said it has provided $2 million for Zika preparedness and another $5.6 million was just allotted, the newspaper reported.
There have been more than 1,400 confirmed Zika cases in the United States, but so far all of them have been contracted through travel abroad -- either by a mosquito bite or by sexual intercourse with someone who had traveled to a Zika-infected area.
CDC officials have said repeatedly they expect to see cases of local transmission of the Zika virus this summer in southern states with warm, humid climates such as Florida, Louisiana and Texas. The virus is typically transmitted through the bite of Aedes mosquitoes.
The CDC has also reported 14 cases of sexually transmitted infections. These infections are thought to have occurred because the patients' partners had traveled to countries where Zika is circulating, the CDC said.
Many infected are symptom-free
Typically, the Zika virus doesn't cause serious illness. Only about 20 percent of patients notice symptoms.
But the virus also has been linked to a rare paralyzing condition called Guillain-Barre syndrome.
The CDC advises pregnant women not to travel to an area where Zika transmission is ongoing, and to use insect repellent and wear long pants and long-sleeved shirts if they are in those areas.