Symptoms & Diagnosis

What is the Zika virus?

Zika is an emerging mosquito-borne virus that usually causes a mild illness or no symptoms at all, but the virus can sometimes have serious complications, especially to developing fetuses.


Is this a new virus?

No, Zika virus has been around for more than 60 years. It was first identified in the Zika forest of Uganda in 1947. Until very recently, it was confined to Africa with occasional small outbreaks in Asia. It slowly spread east, with cases on Easter Island off the coast of South America confirmed in 2014 and the first cases in Brazil in early 2015, and it has spread further throughout South and Central America since then.

Are there any similar viruses?

Zika is a member of the flavivirus family, a group that also includes yellow fever, dengue fever, Japanese encephalitis and West Nile viruses—all of which are transmitted by mosquitoes.

Who can contract Zika?

Anyone who hasn’t yet had the virus is potentially at risk, but the greatest public health threat is to pregnant women and their unborn children.


zika virus symptoms - who is at risk for zika


How is the Zika virus transmitted?

The main way the Zika virus is spread is through the bite of certain Aedes species mosquitoes. Mosquitoes become infected when they bite a human who has the virus, and they are then capable of spreading the virus to other susceptible humans. It’s been shown that the virus can be spread from human to human through infected bodily fluids, but that mode of transmission remains rare.

What are the symptoms of Zika virus?

Between 75 and 80 percent of those infected will not have any symptoms at all. For the unlucky other 20 to 25 percent, common symptoms of Zika include fever, skin rash, red eyes and joint pain. Some patients report muscle pain, general malaise, headache and vomiting. Symptoms, which start between two and seven days after exposure, typically last between two and seven days. Complications are rare, but some cases require hospitalization for supportive care.

zika virus symptoms


What are the complications?

For pregnant women, contracting the virus represents a risk to her unborn baby. Scientists believe that the Zika virus causes miscarriages and microcephaly, a birth defect in which the infant has an unusually small head. For everyone else, an extremely rare complication includes Guillain-Barré syndrome, in which the immune system attacks the body’s own nerve cells, causing problems with muscle coordination and breathing. It can be fatal in rare cases, especially in situations without high-quality intensive care.

Are there tests for Zika available?

The U.S. Food and Drug Administration (FDA) approved a test that is available to laboratories certified by the U.S. Centers for Disease Control and Prevention (CDC). The test looks for the antibodies that Zika causes the body to make, but it’s not 100 percent accurate. A positive test could mean the person was infected with a similar virus, and a negative test doesn’t necessarily mean the person didn’t have Zika—just that the antibody levels were too low for the test to detect.