This story was first published June 13, 2016; it was most recently updated April 5, 2017.
The Zika virus caused birth defects in about 10 percent of the 250 pregnant women confirmed by the Centers for Disease Control and Prevention to have contracted the virus, according to figures published April 4.
The virus, which is principally spread by mosquitoes, fueled public health anxiety last summer after initial reports of the birth defects in Brazil and as the disease spread north. Last year, it triggered a months-long debate in Congress, yielding a $1.1 billion funding package to combat its spread.
Experts believe Zika, which is also sexually transmitted, could return to the United States this summer.
The numbers offer a preliminary window to understand the consequences of this disease — which previously had been the subject of little research — and how many people it affected last year. The CDC, which maintained a Zika Pregnancy Registry across 44 states, reported about 1,300 pregnancies faced possible infection last year.
Women of child-bearing age are believed to be most at risk, although new research has suggested that more monitoring is necessary because some research has shown that symptoms may continue to emerge in babies with prenatal exposure months after they are born. The virus has also been implicated as a potential cause of Guillain-Barre, an autoimmune disorder that causes temporary paralysis and can result in permanent nerve damage and even death. That tie has been supported by research on a 2013 Zika outbreak in French Polynesia and, more recently, by an examination published in the New England Journal of Medicine focused on both Zika and Guillain-Barre’s incidence in Colombia over the past year.
But looking beyond the latest headlines, what’s the real danger? Many doctors expect Zika to pose a renewed concern this coming summer, the peak season for mosquitos. Here’s a quick breakdown of the smart questions to ask and what we do actually know.
I’m a woman of childbearing age. What if I get Zika?
Most of the scariest headlines come from Zika’s potential to cause birth defects — the big one is microcephaly, which severely impairs a child’s brain development. Zika has also been associated with miscarriages. But there are other potential consequences for fetal and infant brain development, vision and hearing, scientists warn. Researchers also don’t know if babies born to mothers with Zika might, somewhere down the line, develop other health conditions, even if they appear healthy upon birth.
This risk should be greatest for women who are actually pregnant. But it’s not always immediately clear if someone has been infected. Symptoms don’t always emerge and, when they do, they often mirror the flu. So if there’s any chance you could conceive in the near future (and remember, almost half of all pregnancies are unintended), you should probably take precautions.
But getting Zika when pregnant doesn’t guarantee you or your child will have problems. An analysis published in May in the New England Journal of Medicine found anywhere between 1 percent and 13 percent of pregnant women infected during the first trimester had children with microcephaly. New research suggests that risk may decline: A June paper in the same journal followed a group of women infected in their third trimester, finding that none had children with the birth defect. But the researchers have cautioned against women letting down their guard until more follow-up is done on the topic.
So, here’s the short answer: The threat of birth defects or pregnancy complications is real. But it is not yet clear who will be affected and why.
I am pregnant. What steps should I take to protect myself?
There’s no cure or vaccine for Zika, and, according to the Centers for Disease Control and Prevention, if you’ve been exposed, you will likely become immune. But that’s not known for sure.
Zika can be transmitted by mosquitoes and through sex. If you are pregnant, the best course of action is to avoid getting bitten. Minimize travel to countries and states where insects are spreading it. If Zika is detected where you live, the CDC recommends wearing long clothes that cover skin and using mosquito repellent.
Repellents containing compounds such as DEET or lemon eucalyptus are best and, if correctly used, shouldn’t pose a danger to pregnant women or fetuses. Peer-reviewed research supports that claim.
What about sex? Zika can stay in semen for extended periods of time. If your partner traveled to an area where the virus is present, the CDC advises avoiding sex — or at the very least, using a condom — for eight weeks. That figure goes up to six months if the man also developed symptoms of the illness. A research letter published in June in the New England Journal of Medicine described how Zika may be transmitted through oral sex. Separate research found it can be spread via anal sex, too. Some speculate the virus can even be transmitted by intense kissing, though evidence is scant.
If you aren’t pregnant but want to be, make sure you and your partner aren’t at risk — either by bites or sexual exposure — before trying to conceive.
I went somewhere where Zika-carrying mosquitoes have been detected, but I feel fine. Can I carry on as normal?
Even if you think you’re fine, take precautions. The problem is that most people with Zika won’t know they were sick. Only about 20 percent of people infected show symptoms. If there’s even a slight risk — say you traveled somewhere with active transmission or had sex with someone else who was exposed — the CDC recommends waiting two months before conceiving. Men, meanwhile, should wait longer. They should take precautions when engaging in sex for six months from either first symptoms or last possible exposure to the virus. The CDC put out that recommendation in September, based on developing information about how long the virus may remain in semen. If you’re sexually active, use effective birth control. Condoms can prevent semen-based transmission. An intrauterine device or the birth control pill will reduce the odds of pregnancy.
Those who show symptoms typically experience fever, a rash, conjunctivitis or aches and pains. If you are experiencing any of those and have reason to suspect Zika, see the doctor as soon as possible for a blood test. The odds of finding the virus are greatest in the first week of showing symptoms. After that, tests are far less reliable, and they might show false positives if you’ve been exposed to other viruses, like dengue, which is transmitted by the same mosquito and therefore also common in areas with Zika. It can also take weeks to hear back on Zika test results. Researchers are trying to develop better diagnostics, and efforts look promising. For now, getting tested is the best option available.
If you test positive for Zika, doctors and the CDC again recommend women wait two months before trying to get pregnant. (That’s a shorter wait period than the two years urged by other affected countries.) Meanwhile, take care of yourself. Rest up, drink lots of fluids and maybe take acetaminophen if you’re suffering aches or a fever. Ask your doctor for advice, too.
I have Zika, and I’m pregnant. What do I do?
This is the hard part. Your child won’t necessarily have a condition, but get in touch with an OB/GYN right away. Your doctor will likely advise regular ultrasounds, though microcephaly can’t be detected until the second trimester of pregnancy. A physician can counsel you on ways to reduce the threat of miscarriage — for which the risk is heightened with Zika — and help keep you up to date on treatments.
This is scary, and it’s a lot of information. How else can I stay up to date?
The science around Zika is constantly changing. Experts say the outbreak is revealing how little we know about the disease. To keep abreast of new developments, the CDC is your best bet: The agency has a fairly comprehensive Zika webpage. The World Health Organization is another good resource. If you want to know what guidance your doctors are receiving, check out the American College of Obstetricians and Gynecologists.
This article was updated to add information from a June 15 New England Journal of Medicine study.