According to the Centers for Disease Control and Prevention (CDC), the Zika virus can be transmitted to people through the bite of an infected mosquito. In February 2016, the World Health Organization (WHO) declared Zika virus infection a global emergency—since October of 2015, more than 4,000 cases of microcephaly (condition in which newborn babies are born with underdeveloped brains) thought to be related to the virus had been reported in Brazil alone.

Prior to 2015, small outbreaks of Zika occurred in areas of Africa, Southeast Asia, and the Pacific Islands, and in May of 2015, the first confirmed cases were found in South America. Since then, locally transmitted cases also have been reported in the Commonwealth of Puerto Rico, and in travelers returning to other areas, including the continental United States. Various health agencies—such as the CDC and the WHO—warn that Zika virus will likely continue to spread.

More research is needed. According to the director general of the WHO in February 2016, priorities are to

  • Protect pregnant women and their babies from the Zika virus, and
  • Control the mosquitoes that are spreading the virus.

WHO reports that several groups are working on Zika vaccines. These studies are in the early stages, and development could take a number of years.

Common symptoms of Zika virus disease include:

  • Conjunctivitis (pinkeye)
  • Fever
  • Joint pain
  • Rash

The virus causes mild symptoms that last from several days to a week in about 1 in 5 people who are infected. Symptoms usually develop within 2 to 7 days of infection. Severe illness is uncommon.

However, Zika infection during pregnancy can cause serious effects—including microcephaly—and poor pregnancy outcomes. In addition, the World Health Organization reports that some countries in which a Zika virus outbreak has occurred also have seen an accompanying rise in Guillain-BarrĂ© syndrome incidence.

As of January 2016, a travel alert is in place for people traveling to:

  • Brazil
  • Colombia
  • El Salvador
  • French Guiana
  • Guatemala
  • Haiti
  • Honduras
  • Martinique
  • Mexico
  • Panama
  • Paraguay
  • Puerto Rico
  • Suriname
  • Venezuela

The Centers for Disease Control and Prevention added Jamaica, Tonga, Aruba, and Bonaire to this list in February 2016, warning that pregnant women should avoid travel to places where Zika virus transmission is ongoing. Pregnant women and women who are trying to become pregnant who must travel to one of these areas should talk to their doctor beforehand and closely follow all recommendations to avoid mosquito bites during their trip. The CDC modified these travel warnings on March 11, 2016 to say that travel limited to areas above 6,500 feet are at minimal risk for Zika transmission from a mosquito. Risk for mosquito transmission is higher below 6,500 feet in elevation.

On February 16, 2016, the Food and Drug Administration (FDA) issued a guideline recommending that people who have traveled to areas with active Zika virus, people who have potentially been exposed to the virus, or those who have had a confirmed case of Zika should be deferred from donating blood. Although no cases of Zika in the U.S. blood supply had been confirmed at the time, blood transmission of the virus is considered a likely possibility.

Zika Transmission

The most common mode of Zika transmission is through the bite of an infected Aedes species mosquito. These mosquitoes, which lay eggs in and near standing water, are aggressive daytime biters that also spread dengue and chikungunya viruses. They become infected with Zika when they bite a person who already has the virus, and then transmit it to others.

Zika also may be transmitted through sexual contact in some cases. The CDC cautions that, until more is known about Zika virus and transmission of the virus, women who are pregnant should abstain from sex or correctly use a condom during sex for the duration of the pregnancy if her sexual partner has traveled to or lives in an area of the world with active Zika infection. Other possible modes of transmission—including from mother to newborn at the time of delivery, through breastfeeding, and through infected blood—are thougth to be extremely rare.

Zika Prevention

There is currently no vaccine to prevent infection with the Zika virus. In areas where the virus (and other mosquito-borne diseases) are present, the following measures can help prevent transmission:

  • Use insect repellents as directed.
  • Treat clothing with permethrin.
  • Wear long-sleeved shirts and long pants.
  • Use air conditioning to cool indoors or window/door screens to keep mosquitoes outside. If necessary, sleep under a mosquito bed net.
  • Empty standing water from outside containers such as flowerpots or buckets.

Read more about How to Prevent Mosquito Bites.

Treatment for Zika

The goal of treatment for Zika virus infection is to relieve symptoms. CDC recommendations include the following:

  • Get plenty of rest
  • Drink fluids to prevent dehydration
  • Take medicines such as acetaminophen or paracetamol to reduce fever and pain
  • Do not take aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs)

Where Has Zika Been Found?

To learn more about the spread of the Zika virus, visit Zika-affected Areas from the CDC.

Sources: U.S. Centers for Disease Control and Prevention (CDC), World Health Organization (WHO), U.S. Food and Drug Administration (FDA); updated by Remedy Health Media, February 22, 2016

Publication Review By: the Editorial Staff at

Published: 24 Jan 2016

Last Modified: 14 Mar 2016