A healthy living blog from Marshfield Clinic

Does Zika cause birth defect, microcephaly?

Close up of a pregnant woman - Birth defects related to Zika virus

Pregnant women with the Zika virus may have babies born with a birth defect known as microcephaly.

As the Zika virus continues to spread, concerns are growing that the virus may be linked to microcephaly, a condition causing a birth defect, primarily abnormally small heads in newborns.

No local mosquito-borne Zika virus disease cases have been reported in the United States, but there have been travel-associated cases. The virus has spread to 30 countries and territories in South and Central America as well as the Caribbean.

Zika is spread primarily through the bite of an infected mosquito. The illness is usually mild with symptoms lasting for several days to a week after being bitten. Symptoms include fever, rash, joint pain and conjunctivitis or pink eye.

Spread by bite from infected mosquito

Pregnant women bitten by infected mosquitoes may have babies born with microcephaly.

“Microcephaly is a birth defect related to an infection in the fetus,” said Dr. Matt Hall, an infectious disease specialist at Marshfield Clinic. Infection-caused birth defects are not a recent phenomenon. “Rubella is a historically-known infection that causes birth defects, but now that we have an effective MMR vaccine to prevent it, most people don’t even know what it is anymore.”

Another concern about microcephaly is it may cause eye defects in fetuses and may affect vision.

Rise in babies born with microcephaly

Since the Zika virus outbreak began a year ago in Brazil, there has been an unusual rise in the number of babies born with microcephaly. The Centers for Disease Control and Prevention (CDC) estimates that 25,000 babies per year are born in the U.S. with the characteristic small head and related complications of microcephaly.

The ratio of these babies to healthy newborns is between 2 and 12 per 10,000 live births. This has led to speculation that Zika and microcephaly are somehow linked to these birth defects. But international health experts point out that microcephaly can have many causes and has not been scientifically proven as the cause of eye defects.

CDC warns pregnant women

Even so, to protect fetuses, the CDC has advised that “pregnant women with a male partner who has travelled to, or lives in, an area where Zika infection is active should refrain from sex or use condoms during sex until the pregnancy is over.”

Hall recommends people planning to travel, especially to Brazil – including those going to the Olympics in Rio de Janeiro this summer – seek travel advice. Visit the CDC site for Zika updates.

“The CDC is anticipating the arrival of Zika in the U.S. and maybe we will see Zika become prevalent in this country,” Hall said. “If and when that happens, public health agencies will have plans in place.”

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