Pregnancy is an exciting time, but it can also be scary — especially when there are reports of mysterious virus outbreaks threatening the health and lives of unborn babies. And for women who have gotten pregnant in 2016 and 2017, fear has been brought to a fever pitch, courtesy of the mosquito-borne Zika virus. Zika virus is infection that can cause a birth defect called microcephaly, a fatal condition in which the baby's head and brain doesn't develop fully.
The general public first became aware of Zika in the early months of 2016, when thousands of babies in Brazil were born with microcephaly. The fear of Zika spread to the United States in August 2016 when a baby in Texas whose mother had traveled to El Salvador during her pregnancy died of Zika-related complications.
The U.S. Centers for Disease Control and Prevention was able to identify 2,549 pregnant women with the Zika virus in Puerto Rico and other U.S. territories between Jan. 1, 2016 and April 25, 2017, and 122 of these women — about 5 percent — gave birth to babies with microcephaly.
New studies have shown that women in their first trimester of pregnancy are at the greatest risk for Zika-related damage to their fetus, though it's possible for a baby to have birth defects due to Zika at any point in a pregnancy. And the CDC is still warning American women to be wary if they're traveling to certain parts of the world.
It certainly seems like we should take the Zika virus very seriously — but how much do we really know about it so far, and what is the risk of microcephaly to American babies?
"Zika virus is a virus carried by the Aedes mosquito and is transmitted to humans via the bite of an infected mosquito," says Dr. Gerardo Bustillo, OB-GYN at Orange Coast Memorial Medical Center in Fountain Valley, California. "First discovered in Ugandan rhesus monkeys in 1947, it has been associated with outbreaks in different parts of the world. Zika virus is related to other mosquito-borne viruses, such as dengue virus and West Nile virus. Zika first appeared in the Western Hemisphere in early 2014 on an island off the coast of Chile. Since then, it has been detected in several countries in Central and South America."
And of course, now we know it's popped up in the U.S. as well, and the CDC officially warning American women to steer clear of an area of Miami where mosquitoes are believed to be infected last year. The Florida Department of health, however, has reported that the number of Zika cases in their area has dropped in the past year — in 2016 alone there was a reported 264 pregnant women with lab-evidence of Zika, while there has only been four reported cases so far in 2017.
Dr. Sherry Ross, OB-GYN and women’s health expert at Providence Saint John’s Health Center in Santa Monica, California, says experts are still learning the effects of this virus on children and non-pregnant adults. “Only 1 in 5 infected people will show any kind of symptoms, and the majority will only have mild flu-like symptoms,” she says, referring to the fever, conjunctivitis, rash and joint pain. "However, I would still encourage prevention of being exposed to this virus to all age groups."
Other common symptoms of the virus, which appear two to 12 days after a mosquito bite, include muscle aches, headache, pain behind the eyes and generalized weakness, Bustillo says. The good news is that severe disease is uncommon: The illness is usually mild and symptoms resolve after two to seven days.
These facts don't, of course, take away from a terrifying one: Zika can seriously affect pregnant women, regardless of what trimester they're in, Ross says. "If you become infected with this virus during pregnancy, it has been associated with birth defects including a small, shrunken brain and malformed head known as microcephaly," she says. "This virus can be transmitted to the fetus as well."
But what exactly is microcephaly, and what causes this rare condition?
“Microcephaly is a head circumference (measured in a fetus or infant) that is significantly below the mean for a given age (or gestational age in fetuses) and sex," Bustillo explains. "It can be the result of a multitude of causes, including genetic abnormalities, brain injury from exposure to toxins or infections during gestation (such as Zika infection) and birth complications. In at least 40 percent of cases, there is no known cause. The severity of neurologic impairment is generally related to the severity of microcephaly, and may be significant. The exact mechanism by which Zika causes microcephaly, and the magnitude of the resulting damage, is still being investigated.”
Pregnant women who have recently traveled to an area with Zika virus transmission and have symptoms of the infection (fever, rash, joint pains and/or pinkeye) should have blood testing for Zika virus infection, Bustillo says. "All pregnant women with a relevant travel history, [regardless] of the presence of symptoms, should have fetal evaluation, with serial ultrasounds looking for microcephaly," he says. "If the ultrasound suggests the presence of microcephaly, amniocentesis may be performed for Zika virus testing."
Zika has been found in breast milk, and the Centers for Disease Control and Prevention has confirmed the virus can be transmitted during labor, sexual contact, blood transfusion or lab exposure, but infant Zika virus infection associated with breastfeeding has not been reported. And the CDC continues to encourage women who may have been exposed to Zika to breastfeed.
"Current evidence suggests that the benefits of breastfeeding outweigh the theoretical risk of Zika virus infection transmission through breast milk. CDC encourages mothers with Zika virus infection and mothers living in areas with ongoing Zika virus transmission to breastfeed their infants," it says on the CDC website.
Without a vaccine or treatment yet, Ross says the best prevention method is to avoid traveling to areas where Zika outbreaks are occurring. The CDC regularly updates its website, and there are currently some two dozen countries on the list, plus areas in the U.S. itself including Texas and Florida. If you are traveling to these areas, it's crucial that you wear protective clothing and mosquito repellent.
There is an incubation period for the Zika virus of three to 12 days. If you experience symptoms associated with the virus, visit your doctor, and treat the symptoms as you normally would. "Infected persons should get plenty of rest, drink plenty of fluids to prevent dehydration and treat fever with common medications," Bustillo says. "The best way to prevent infection is to avoid mosquito bites. Personal protective measures include applying mosquito repellent, wearing long sleeves and long pants and staying indoors. Window and door screens and mosquito nets help to minimize contact between mosquitoes and people. Since mosquito larvae breed in standing water, every effort should be made to avoid allowing standing water to collect outdoors, as in buckets, bottles and flowerpots."
Originally published January 2016. Updated June 2017.