Tropical diseases used to be confined to the tropics (and to some unlucky travelers after they got back home). But more illnesses like Zika — a mosquito-borne virus that may have caused a rash of birth defects in Brazil — are moving north and may eventually hit the United States.

Zika virus is among the tropical ills that are cropping up in areas where they were previously unknown. It’s one of the arboviruses — diseases spread by mosquitos, ticks, sandflies and other arthropods — that include chikungunya and West Nile virus.

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As arboviruses go, Zika is a mild one. No one has died from it as far as experts know. It can cause a fever, rash, joint pain, and conjunctivitis (pink eye), sometimes accompanied by muscle pain, headache and vomiting, according to the Centers for Disease Control and Prevention (CDC).

But scientists have recently found that a handful of patients apparently go on to develop Guillain–Barré syndrome, an autoimmune disorder linked to nerve damage and paralysis. As Scott Weaver, a mosquito-borne disease expert at the University of Texas at Galveston told Scientific American, “This is a pretty troubling finding.”

Scientists fear Zika virus may also cause microcephaly, a birth defect in which babies are born with abnormally small skulls and brains. This can cause mild to severe brain damage according to the Cleveland Clinic. Brazil declared a state of emergency after the number of babies born with the condition jumped from 157 in 2014 to 2,400 in 2015. Zika virus became the leading suspect after it was detected in an infant with microcephaly and in the amniotic fluid of two mothers whose babies had the condition, according to news reports.

Thanks partly to climate change and global travel, scientists say, the virus is expected to join other serious insect-borne illnesses that have recently invaded the United States. These include dengue fever and Chagas, a disease caused by blood-sucking insects known as “kissing bugs,” as well as tropical diseases, such as chikungunya, that are showing up in infected American travelers.

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Until May 2015, Zika had never shown up in this hemisphere (except on Easter Island). It’s now found in 14 Latin American or Caribbean countries, and Puerto Rico reported its first confirmed case in December 2015, according to the CDC. Other outbreaks have taken place in Africa and Southeast Asia. Zika has not yet been reported in the United States, the agency notes, but some cases have recently shown up among returning travelers.

There’s no vaccine or antibiotic for Zika disease. So if you’re traveling to an area where Zika is common (see the CDC's map), the CDC encourages you to take precautions against the mosquitoes that carry it by:

  • Using insect repellent
  • Wearing long sleeves and pants
  • Staying in places that have air conditioning or windows and door screens

Some travel clinics recommend applying insect repellent that contains 30 percent DEET to exposed skin and clothing and using mosquito nets over cots, playpens and strollers to protect babies.

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Diana is an award-winning writer and editor with more than 20 years' experience in magazine, video, book and digital journalism, with a specialty in health coverage. She was a longtime writer and news editor at the Center for Investigative Reporting; has written for publications from the Washington Post to the Times of London syndicate; and has served as a senior and/or consulting editor at Time Inc. Health, Hippocrates, HealthDay News Service and Reporting on Health. She was also editor in chief of Consumer Health Interactive, a national health and medical web site, and has reported on finance for Blueshift Research and PBS Frontline. Before joining SafeBee, she was editor of Bioenergy Connection, a national magazine about bioenergy at UC Berkeley. Her favorite safety tip: Wear a bike helmet.