Should You Get Tested For Zika Virus? A Flowchart

This should settle it. For now.

UPDATE: The CDC's guidelines for pregnant travelers returning from an area with Zika virus transmission changed Feb. 5. See the latest advice for pregnant women who may have been exposed to the virus but aren't experiencing symptoms.

News about Zika virus -- the tropical, mosquito-borne disease that may be responsible for birth defects and an autoimmune syndrome -- is probably all over your Facebook feed, radio broadcast or TV screen. Or maybe you're all set to go to that long-awaited wedding or bachelorette party in Mexico, and your mom keeps sending you newspaper clippings in an effort to get you to cancel your trip.

As paranoia builds, you may wonder: should I be worried about Zika virus, and should I get tested for Zika virus when I get back from my trip?

Some background: Zika virus cases didn't appear in Latin America, where it's currently spreading, until May 2015. Then, in Oct. 2015, the Brazilian government alerted the World Health Organization to an alarming increase in infants born with microcephaly, a condition in which a fetus' brain doesn't develop properly in the womb and the baby is then born with an abnormally small head.

Between Oct. 2015 to Jan. 2016, over 4,000 babies in Brazil have been born with this condition, which can cause lifelong intellectual disability, developmental delays and even death. This is a sharp increase from the years 2010 to 2014, when Brazil averaged only about 156 cases of microcephaly each year. The country also saw an uptick in cases of Guillian-Barre syndrome, a condition that causes temporary paralysis and, in rare cases, death.

Besides these possible but as-yet-unconfirmed disease links, one of the most disturbing aspects of Zika virus is that not everyone who gets it even knows they have it, and we don't know what this means in terms of its effect on fetuses in utero.

The virus’ symptoms are mild. They include a rash, fever, joint pain and red eyes that last between two and seven days, and are in fact so mild that some people may not experience any symptoms at all.

The World Health Organization estimates that one in four infected people may not experience symptoms, while other experts think the proportion is reversed: The U.S. Centers for Disease Control and Prevention cites studies that say that up to 80 percent of people who get Zika virus don’t get any symptoms and thus don't know they have it.

Step 1: Did you travel to an area where Zika virus transmission is ongoing?

What if you’re a recent traveler from one of the 24 Zika-affected countries or territories about which the CDC issued health warnings? What happens if you know you got mosquito bites, but aren’t experiencing any symptoms?

If you are healthy and not pregnant, you probably have nothing to worry about, most experts say. Dr. Michael Klompas of the Division of Infectious Disease at Brigham and Women’s Hospital in Boston says that because there’s no specific cure for Zika virus, there’s no benefit to figuring out if an asymptomatic person has it. In other words, there’s no symptom to treat, and we have nothing to treat it with anyway.

If you're a recent traveler who does have any one of the four symptoms, you should seek a doctor's help regardless of whether or not you think it's Zika virus, as the disease shares symptoms with other tropical or mosquito-borne diseases like malaria and Chikungunya virus and more run-of-the-mill but serious things like measles, rubella and enterovirus.

The doctor should then determine whether or not to request a Zika virus test for you based on your travel dates, activities and symptoms, according to CDC guidelines.

Step 2: Are you pregnant?

The stakes are higher for pregnant travelers, who, if infected with Zika virus, may run the risk of giving birth to a child with microcephaly.

But the CDC generally steers asymptomatic pregnant travelers straight to ultrasounds rather than testing, suggesting that they schedule regular visits to monitor fetal growth. If microcephaly or other head abnormalities are detected, then the traveler should get tested for Zika.

Symptomatic pregnant travelers should get tested for the virus only if they experience two or more of the disease’s common symptoms during or within two weeks of travel to an area with local transmission, or if recent ultrasounds indicate that their fetus may have microcephaly or other cranial abnormalities, according to CDC guidelines.

This may sound lax considering the possible link between Zika and birth defects. Shouldn't every pregnant woman who may have been exposed be tested, you may wonder (and some experts have)? As the New York Times points out, microcephaly is only detectable by ultrasound after the second trimester, which means asymptomatic mothers may have to wait a very long time before seeing if their child is at risk for the condition.

Health authorities may be hesitant to recommend testing for asymptomatic pregnant moms because the U.S. doesn't have the laboratory capacity to test every pregnant woman who travels to Latin America and the Caribbean during the nine months of her pregnancy. Also, there's no evidence to know either way whether noticeable Zika symptoms play a role in birth defects, or whether mere presence of the virus poses a danger.

Despite these ambiguities, Stephen Morse, an epidemiology professor at the Mailman School of Public Health of Columbia University, supports the CDC’s approach to testing for pregnant women. He says that while he’s sympathetic toward those who are coming back from a Zika-affected country with mosquito bites, probably the best thing they can do is to get standard prenatal care, which includes sonograms, early on.

"The usual antenatal testing should pick up any abnormalities, including [microcephaly]," said Morse. "That’s probably going to be much more informative than testing for the virus."

Step 3: Is a test available to you?

There’s also the question of availability. There are no commercially available Zika virus tests, and only a handful of places in the U.S., including the CDC, are performing them. This means that most doctors who order a test will have to send it off to a specialized laboratory with assistance from their local or state health department.

Dr. Anna Durbin, an associate professor at Johns Hopkins Bloomberg School of Public Health, says that if pregnant travelers sought Zika virus tests just because they got mosquito bites, the requests would “overwhelm all systems.”

It's a troubling set of circumstances for pregnant Americans who were either in a Zika-affected country when travel warnings were issued or who absolutely cannot abide by the agency's advice to postpone travel. But for now, the official advice for pregnant travelers, barring any personal symptoms, is to watch and wait on what ultrasounds are turning up on their fetuses.

So far, Brazil, Colombia, El Salvador and Jamaica have advised women in their countries to postpone pregnancy until the Zika epidemic is over. The U.S. has also advised all pregnant women to postpone travel to a Zika-affected country, and for women who want to become pregnant to seek advice from their healthcare provider first.

This story has been updated with the latest count of babies born with microcephaly in Brazil.

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