So – how worried should you be? And what is Zika, anyway? Here’s what you should know.It’s a virus that’s related to other mosquito-borne diseases like dengue and chikungunya. People can become infected with Zika after being bitten by a certain mosquito (the Aedes species to be exact — more on that later).The virus isn’t new — at least, not to many around the world. Zika was first discovered in Uganda in 1947, and up until last year, the virus mainly hung out in parts of Africa, Southeast Asia, and the Pacific Islands. Then, sometime around May 2015, the virus hopped over to the Americas.Since it’s just recently arrived in the Western Hemisphere, those of us on this side of the world haven’t built up an immunity to Zika yet, and we might be particularly sensitive — in fact, experts say that’s one possible reason why it’s spreading so rapidly.About 80% of people who catch the Zika virus won’t show any symptoms at all; the other 20% might have a mild fever, a rash, some joint pain, or conjunctivitis. (Muscle pain and headaches can occur too .) Whatever the symptoms, they’ll likely only last for a few days, probably a week at most. In most cases, the symptoms are manageable, and don’t require hospitalisation.After that, it clears out of your system, and that’s the end of it, says Daniel Lucey , MD, MPH, an adjunct professor of microbiology and immunology at Georgetown University Medical Center.The reason so many people are talking about this right now is because experts are worried about a possible link between the Zika virus and a birth defect called microcephaly. (We say “possible,” as according to the Centers for Disease Control and Prevention (CDC), it’s still just an “association” — albeit one that’s looking more and more certain every day.) Microcephaly is characterised by a smaller-than-average head, and usually indicates an underdeveloped brain as well. This can set these babies up for a lifetime of problems, including vision loss, seizures, learning disabilities and more.This is a BFD considering that previously, experts thought that Zika mostly caused minor symptoms, rarely required hospitalisation, and ultimately resolved itself on its own.Brazil has been dealing with a Zika virus outbreak since early 2015, and in September of last year, there was a huge jump in the number of reported cases of microcephaly — possibly an increase of 20 times the average amount . Further testing revealed that the virus was found in the amniotic fluid of two women whose foetuses had microcephaly, and another report on 35 women showed that all of them had either lived in or visited regions that were known to be affected with Zika.Given the growing certainty about the link to birth defects, and the spread of the virus, experts are rightfully flagging Zika as a huge concern for everyone right now. Governments in El Salvador, Colombia, and Ecuador are going so far as to urge women to put off getting pregnant completely for months — even years in El Salvador’s case, in an effort to prevent potential birth defects.With the disclaimer that it’s changing fast ( Puerto Rico just reported its first locally acquired case), just know the CDC has issued a travel alert for 22 countries and territories in the Americas. An “alert” from the CDC means certain people (in this case, pregnant women) should avoid travelling there, and anyone should take “enhanced precautions.” It’s one step below a travel “warning,” which means the risk is high enough that the best advice is to completely avoid a trip there.As of now, the list of countries with a CDC alert for Zika includes: Cape Verde, Samoa, Barbados, Bolivia, Brazil, Columbia, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname, U.S. Virgin Islands, and Venezuela.The CDC says that pregnant women should delay visiting those areas if possible. ( Some airlines are reportedly offering refunds on tickets to Zika-affected countries if you’ve already booked.) If you’re currently trying to get pregnant, the CDC says to talk with your doctor before finalising your travel plans. And if you’re pregnant and you must travel, take precautions against mosquitoes and watch for symptoms. If you start to feel sick within two weeks upon your return, you'll need a Zika virus test.As for all non-pregnant travellers to these countries, the best thing you can do is try to avoid being bit by a mosquito. That’s easier said than done, of course, but you might have more options that you think: Wear long sleeves, use EPA-registered insect repellent, and get rid of (or stay away from) any standing pools of water, which are fertile breeding grounds for mosquitoes.And finally, if you’ve recently been travelling to any of the countries on the CDC’s list and you start feeling sick, definitely see a doctor.