Zika 101

What you need to know about the Zika virus.

The Zika virus has regularly made headlines since 2015 due to its rapid spread and connection to the rare birth defect microcepahly, leading the World Health Organization (WHO) to declare it a global health emergency in February 2016. In June, the Centers for Disease Control and Prevention (CDC) reported 756 cases in the U.S., including 234 pregant women. With the Summer Olympics approaching this August in Rio de Janiero, Brazil, the hardest hit region, the world is keeping a close eye on how, if at all, this will affect Zika's reach.

In the meantime, here's everything you need to know in order to protect yourself. This information is accurate as of June 2016.

Aedes aegypti mosquito

Aedes aegypti mosquito

SANTO DOMINGO, DOMINICAN REPUBLIC - FEBRUARY 10: An aedes aegypti mosquitoes that carries the Zika virus is seen at a laboratory of the National Center for the Control of Tropical Diseases (CENCET) in Santo Domingo, Dominican Republic on February 10, 2016. (Photo by Stringer /Anadolu Agency/Getty Images)

Photo by: Anadolu Agency/Getty Images

Anadolu Agency/Getty Images

What is the Zika virus?

Although Zika hasn’t made headlines for that long, it’s not a new virus. It was first discovered in a monkey who lived in Uganda’s Zika forest in 1947, but the first major outbreak didn’t occur until 2007. It’s believed that the current outbreak stems from an infected person who traveled from French Polynesia to Brazil and was bitten by a local mosquito, which in turn bit and infected others. Infected Aedes aegypti mosquitoes (which also carry dengue, chikungunya and yellow fever) spread the disease, but, to a lesser extent, Zika can also be spread by unprotected sex or a blood transfusion.

WHO has confirmed that since the virus has been found in saliva, that is another possible way to contract it. However, Dr. William Schaffner, an infectious diseases specialist at Vanderbilt University School of Medicine, says that it’s not clear if Zika can be transmitted through saliva in terms of kissing. At this point there are still a number of unknowns surrounding Zika.

What are the symptoms?

It’s more likely for someone to be infected without knowing it, since about 80 percent of people don’t exhibit any symptoms. For those who do, symptoms are generally mild and typically cause fever, rash, muscle and joint pain and red eyes, which could last about a week. The only way to know for sure is to get tested, since the symptoms are similar to other illnesses, like the flu.

However, Jeanne Sheffield, M.D., professor of gynecology and obstetrics at The Johns Hopkins University School of Medicine, says that since testing is limited, only people who have traveled to a Zika-affected area and are showing symptoms would receive it. The exception would be pregnant women, who would be tested whether or not they’re symptomatic.

Who is at risk?

The main concern is for pregnant women, since Zika has been linked to serious birth defects, including microcephaly. This potentially fatal birth defect stunts brain growth and causes underdeveloped heads, which in turn affects everything from intellectual development to vision and hearing. It’s unknown what percentage of infected pregnant women will develop birth defects. The WHO says Zika-related birth defects are more likely if the virus was contracted in the first and second trimesters, but Dr. Sheffield says all trimesters are at risk.

Another concern is that a small number of people develop Guillain-Barre syndrome, a rare illness that causes muscle weakness or paralysis. At present there’s no vaccine or cure.

Current situation in the U.S.

As of June 2016, the CDC reports there are 756 cases in the U.S., but none were acquired locally. Of those, 11 cases were sexually transmitted. The highest numbers are in New York (174) and Florida (141). A new study has revealed that there are currently 234 pregnant women in the U.S. with Zika. So far three babies have been born with Zika-related birth defects, and three more died before birth. The number of infected travelers returning to the United States have been climbing at a steady clip, but it’s impossible to know the true count of Zika infections, whether here or abroad. “The big question is what is the overall number? Nobody knows,“ says Dr. Sheffield. “I can say, out of 200 people that were tested, this many are positive, but there may be 100,000 people that should’ve been tested, but only tested 200 because of criteria.”

Current situation abroad

WHO is reporting that Zika is currently in 60 countries and territories, up from just 24 in January 2016. The CDC has compiled a map showing which countries are currently experiencing an outbreak. Canada is among the countries not at risk since it doesn't have Aedes mosquitos. Until recently, officials believed Chile didn't contain the Zika-carrying mosquito either; WHO confirms that one dead Aedes aegypti was found in Arica, Chile's northernmost city. However, a spokesperson says while health officials are seeking more, large numbers aren't likely to be found and the country isn't considered at high risk.

The WHO declared Zika a global health emergency back in February due to increased rates of microcephaly, birth defects and Guillain-Barre syndrome. It has affected the majority of Latin America and the Caribbean, although Brazil has been hit hardest with WHO reporting almost 40,000 confirmed cases, and almost 160,000 suspected ones. Of those, there are 1,581 confirmed cases of babies born with microcephaly and other birth defects believed to be Zika-related. As of June 2016 the CDC lists Brazil at Level 2, calling to “practice enhanced precautions.” These includes vigilant mosquito bite prevention for the general public. Women who are pregnant or trying to become pregnant are advised to delay travel.

What are the odds of Zika spreading to the U.S.?

Aedes mosquitoes are common in the states; the CDC has mapped their potential range. As a tropical mosquito, they’re more likely to be found in the southern half of the country, and possibly further north in the summer.

A WHO spokesperson says that local transmission depends on how many Aedes aegypti mosquitoes bite someone with Zika, and then go on to bite others. However, Dr. William Schaffner, an infectious diseases specialist at Vanderbilt University School of Medicine, predicts a limited spread in the U.S., in part because most people live in air-conditioned homes with the ability to keep windows and doors closed. In addition, he says Zika is likely to be “very localized and rapidly contained by a brisk and comprehensive public health response.” Experts note this would include intense mosquito spraying.

What about traveling to the Olympics in Rio this summer?

Despite a petition signed by 239 members of the international medical community, academics and more to cancel this year’s Summer Olympics in Rio, WHO experts reaffirmed on June 14 that the Olympics don’t pose an increased risk for spreading the virus. Dr. Schaffner points out that a significant number of people already travel between the U.S. and Zika-affected areas. He also notes the Olympics will occur during winter in the Southern Hemisphere, when mosquitos aren’t as active.

What are the odds of Zika spreading to Europe?

Europe’s mosquito equivalent to Aedes aegypti is Aedes albopictus, which can also carry Zika.

In a statement on May 18, WHO Regional Director for Europe Dr. Zsuzsanna Jakab said, "The new evidence published today tells us that there is a risk of spread of Zika virus disease in the European Region and that this risk varies from country to country." The press release put the odds of Europe facing a low to moderate risk as of now, and the risk is higher where Aedes mosquitos are found, such as Spain.

How to protect yourself:

Aedes mosquitos are typically found indoors and bite during the day. The CDC compiled a full list of precautionary measures to take, which include covering exposed skin, wearing permethrin-treated clothes and using insect repellents that are EPA-registered and contain either picaridin, IR3535, lemon eucalyptus oil or DEET. Dr. Shaffner says it’s important to use insect repellent before going to sleep as well. “A facetious comment is the fragrance of the year is DEET.”  

While it’s not always possible, the CDC also recommends staying in air-conditioned places and avoid opening windows. The WHO also recommends wearing light-colored clothing, since darker colors attract mosquitos.

Should I travel to Zika-affected countries?

The short answer is, it depends. The longer answer is that a number of factors need to be taken into consideration:

Are you pregnant? The CDC and WHO are advising pregnant women to delay traveling to countries where outbreaks are occurring, including the 2016 Olympics in Brazil. As of June 2016 there is no cure for microcephaly. If you’re pregnant and must travel to an area with a Zika outbreak, consult a doctor beforehand. The CDC has confirmed that pregnant women can use any EPA-registered bug sprays — even DEET. Men should follow safe sex practices or abstain from sex to prevent the possibility of transmitting Zika. “Zika’s pretty nasty, and the more we learn about it, the nastier it becomes,” says Dr. Shaffner concerning birth defects.

Are you trying to get pregnant? The CDC advises following the same advice as the general public, in addition to getting a doctor’s opinion. However, Dr. Shaffner is erring on the side of caution by advising all women of child-bearing age to avoid Zika-affected areas. “Maybe this summer is a wonderful time to go to Rome.”

What is the nature of your trip? Dr. Shaffner notes there may be a lower risk of contracting Zika if you’re staying at an air-conditioned hotel where the windows and doors are kept closed.

What if I decide to cancel my travel plans?

There’s no standardized policy on Zika, so be sure to check with individual hotels and resorts, airlines, cruise lines and insurance plans for the refund policy.   

What to do if you suspect you have Zika:

WHO only recommends seeing a doctor if symptoms worsen. The CDC suggests visiting a doctor if you experience a fever with rash, joint pain or red eyes, along with taking acetaminophen, resting and drinking plenty of fluids. A blood test can confirm if you've been infected, but it's currently limited to pregant women, along with men and women who have traveled to a Zika-affected area and display symptoms. The WHO confirms that developing additional testing for the virus is a priority.


Since most people who get bitten by a Zika-infected mosquito won’t have any symptoms, they become unwitting carriers. Although Zika is believed to stay in the bloodstream for about a week after getting bitten, the CDC cautions, “Even if they do not feel sick, travelers returning to the United States from an area with Zika should take steps to prevent mosquito bites for three weeks so that they do not spread Zika to uninfected mosquitos.”

In addition, the CDC advises women who traveled to a Zika-affected country to wait at least eight weeks before getting pregnant, whether or not they had symptoms. Since Zika can linger in sperm for up to six months, asymptomatic men are advised to use condoms for eight weeks, and six months if they had symptoms. If their partner is pregnant, they should either use condoms or abstain from sex until after the baby is born.

Dr. Sheffield says it’s unknown how long the virus stays in the body, but the CDC recommends getting tested within two weeks of suspected symptoms. After that time frame, Dr. Sheffield says antibodies can be tested for Zika.

The good news is that the CDC believes one becomes immune to the virus after getting infected, and that there’s no risk of microcephaly or birth defects in future pregnancies.

Is a vaccine or cure in the works?

Yes, Inovio Pharmaceuticals has just been given FDA-approval to enter Phase 1 clinical trials, and several more organizations, including the National Institutes of Health (NIH), are close behind. Experts predict that a fully approved vaccine for the general public is at least a year away, as of June 2016.

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