A year ago, the World Health Organization (WHO) took the unusual step of declaring an international public health emergency regarding the mosquito-borne Zika virus and its suspected link to the birth defect microcephaly. The move by WHO highlighted the seriousness of the outbreak, coordinated the global effort against the virus and helped countries where it had shown up to get access to the funding they need to fight Zika. By this February, Zika had been reported in 76 countries – Vietnam being the latest; the majority of hotspots are in the Americas. 

Brazil was the first country to raise the alarm in May 2015, when the current outbreak began. Doctors first noticed an increase in Guillain-Barré syndrome, a rare autoimmune disorder. Then, in October, there was a surge in the number of babies born with microcephaly, a birth defect that results in an unusually small head and in most cases, some degree of brain damage. As of late January 2016, 4,180 cases had been reported in Brazil, according to the Washington Post, which also noted that some may not end up being microcephaly or Zika-linked.

Last April brought reports that Zika might be related to other neurological disorders in adults, including two types of encephalitis and a spinal cord inflammation called myelitis.

This past November, WHO lifted the designation of a “public health emergency of international concern,” but acknowledged that the fight against Zika is far from over. Scientists remain hard at work on developing a vaccine (see Zika Vaccine: How Long Do We Have to Wait? for details) and understanding more about the virus and how it affects babies and adults. For now, however, the focus continues to be on prevention and treatment.

Zika in the United States

As of February 8th, 5,001 Zika cases have been diagnosed in the U.S. New York has had the highest number of cases, followed by Florida and Texas. Early on, Governor Rick Scott of Florida declared a health emergency in four Florida counties where nine people had been found to have Zika. With the February 2016 discovery of 14 new cases of possible transmission of Zika by sexual contact (see below), American authorities were concerned that, as the weather warmed, the disease could affect those on the U.S. Gulf Coast, according to a New York Times interview with Dr. Peter J. Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine. Subsequent computer-modeling research enhanced that concern.

Zika has now been found in all 50 states, but the vast majority of cases – 4,780 – have been connected with travel. Only Florida and Texas have reported documented cases of viral transmission from a mosquito to a human. Although the outbreak in the U.S. has, so far, been limited, it raises the question: How dangerous is Zika – and how can you protect yourself from getting it? What should you do if you are pregnant or planning to get pregnant? And what about travel?

Here’s a quick review of what’s known about the virus, how it spreads, who’s at highest risk and how to avoid it.

The Source, Symptoms and Sex

Zika is one of the so-called flaviviruses (dengue, West Nile and yellow fever are others) that are primarily spread by Aedes mosquitoes. Aedes aegypti and Aedes albopictus, two types of these mosquitos, are common in the Americas, including in the southeastern and south-central states and in Hawaii. The virus gets its name from the Zika Forest of Uganda, where it was first isolated in a febrile rhesus money in 1947. There were few cases of Zika in humans until 2007, when an outbreak occurred in Micronesia. Since then, there have been outbreaks in 2013 (French Polynesia) and 2014 (New Caledonia, Cook Islands, Easter Island). The outbreak in Brazil represented the first widespread event in the Western Hemisphere. 

Signs of Zika include fever, aching joints, a rash, conjunctivitis and sometimes overall-body aches, headache and vomiting. These symptoms usually last a week. “But only 20% of those infected with the virus exhibit these signs,” says Robert Glatter, M.D., emergency physician at Lenox Hill Hospital in New York City. This obviously makes Zika “difficult to diagnose.”  There’s no widely available test for the virus, no medicine to take for it and no vaccine against it – although various groups are working on vaccines and hope to have one to test in clinical trials this year; guesstimates for getting a vaccine into production range from one to five years. (For related reading, see How Pharmaceutical Companies Price Their Drugs).

Despite some data from Brazil that have found the virus in saliva and urine – and now, even tears, say U.S. researchers – you probably can't catch the virus from somebody else the way you catch a cold. Anthony Fauci, head of the National Institute of Allergy and Infectious diseases told NPR that "we need to be careful that we don't jump to any conclusions about transmissibility."

Having sex is a different issue: The virus has been found in semen, and, as of January 6th, 38 cases of sexual transmission have been confirmed by the U.S. Centers for Disease Control and Prevention. The CDC has issued extensive guidelines for couples on how to avoid passing on or getting Zika through sex – basically, by using condoms or abstaining from sex. (Read the guidelines for the specific types of sexual contact that require protection.)

In addition, last August, the Food and Drug Administration recommended screening for Zika virus in all donated blood in the U.S.

About those mosquitoes: They bite mostly during the day, can bite multiple times and like to breed in small amounts of water – as small as the amount pooled in a candy wrapper or a tossed Styrofoam container. When the weather’s hot, they’re more active and the virus develops more rapidly in their bodies, which makes summer a prime time for infection. Remember, it’s summer now in the Southern Hemisphere, where the virus has been active.

Danger to the Unborn

Women who are pregnant or trying to get pregnant are at the greatest risk from Zika because of its link to microcephaly and apparent placental transmission. “The riskiest time is the first trimester,” says Dr. Glatter, “when women may not even know they are pregnant.”  The CDC has laid out FAQs for pregnant women or women who are trying to get pregnant; its recommendations are updated as more information is gathered. Pregnant women in any trimester are advised not to travel to areas where Zika is present. If you’re trying to get pregnant, speak to your doctor if you plan to go to one of these hotspots and take steps to avoid mosquito bites (see below).

It is possible to test the fetus for Zika in utero, but it's not an easy procedure, and few labs are equipped to do it. It’s best for pregnant women to talk to their doctors about how to proceed. 

Zika Danger to Adults

An April 2016 report in CNBC detailed growing concern that Zika exposure was leading to a widening range of brain problems in adults – and that, according to a paper by WHO researcher Mary Kay Kindhauser, the virus itself “appears to have changed in character,” transitioning from a mild infection to one that causes “large outbreaks linked with neurological disorders.”

Two different mechanisms may be operating in how Zika infections lead to brain-cell problems. Guillain-Barré is an autoimmune illness in which the body attacks itself after an infection. By contrast, the newly identified brain and spinal cord disorders are infections that directly attack nerve cells and can cause temporary paralysis, or tingling, prickling and burning sensations, among other symptoms.

How to Protect Yourself – and Others

For most adults and kids in the U.S., the risk from Zika is still thought to be low. However, you can lower your risk even further:

  • Avoid traveling to any of the areas where Zika is circulating; visit the CDC website for the latest list (and prevention advice). If you have visited one of them, don’t donate blood for a month after your return.
  • If you can’t avoid going to one of these regions, avoid mosquitoes and their bites: Use an EPA-registered insect repellent with DEET, picaridin, oil of lemon eucalyptus (OLE), or IR3535 (these are safe for pregnant and breast-feeding women to use, but not for babies under two months old); wear clothing with long pants and long sleeves; sleep in a room with air conditioning (or under a mosquito net if you’re outdoors).
  • If your partner/spouse has been to an area with Zika, the CDC recommends using condoms – for eight weeks if the traveler is female or for six months if the traveler is male (because Zika stays in semen longer than in any other body fluid).
  • In particular, pregnant women should always use a condom when having sexual contact with a man who has been in a Zika-infected area – or abstain from sex throughout the pregnancy.
  • If you do come down with Zika, try to avoid getting bitten by mosquitoes to protect others from getting your illness (mosquitoes can pick up the infection from your blood and pass it on).
  • If your home is in an area where the Aedes mosquito thrives, discourage their breeding by eliminating any standing water – in watering cans, old tires, empty flower pots, etc.
  • Also, check out Zika: Study Says This Device Could Protect You for new research on whether using a wearable anti-mosquito clip-on could help.

Travel Plans?

Considering all of the cautions on Zika, is that winter getaway to a warm-weather spot or that spring or summer destination wedding a good idea? First, it’s important to note that the CDC distinguishes between areas where Zika is epidemic – countries and territories with current outbreaks, numbering 66 right now – and where it’s endemic – places that have had outbreaks in the past but have few, if any, current ones (a total of 10).  Right now, for instance, the entire Caribbean is in the epidemic category. If you aren't pregnant (or planning to be; that includes partners), take the precautions listed above to avoid mosquito bites or head to higher elevation: Mosquitoes that carry Zika usually don’t live above 6,500 feet. Check the CDC website for travel information as you make your plans (you can text PLAN to 855-255-5606 to receive Zika updates for your destination).

The Bottom Line

Based on where the Aedes mosquito is prevalent and on current weather patterns, the odds of there being an epidemic of Zika in the U.S. are low right now. But stay tuned to the news: If there’s one thing for certain, it’s that recommendations and advice will evolve as researchers learn more about Zika – and how to fight it.