10 Questions About Zika: The CDC Answers

Denise Jamieson, MD, MPH


February 17, 2016

Editorial Collaboration

Medscape &

What Is Zika Virus?

Zika is a disease caused by Zika virus, which is spread to humans primarily through the bite of an infected Aedes species mosquito. The Zika virus is closely related to dengue, yellow fever, Japanese encephalitis, and West Nile viruses.[1]

Other Than Through Mosquito Bites, How Can Zika Virus Be Transmitted?

Although Zika virus is primarily transmitted through the bite of infected Aedes mosquitoes, there are several other modes of transmission[2,3]:

  • Maternal/fetal

    • Intrauterine

    • Perinatal

  • Other

    • Blood transfusion

    • Laboratory exposure

    • Organ or tissue transplantation

  • Sexual transmission

Where Did the Zika Virus Come From?

In 1947, Zika virus was first found in a monkey in Uganda. Before 2007, only sporadic human disease cases were reported in Africa and Southeast Asia, although additional cases were likely to have occurred and were not reported. In 2007, the first outbreak of Zika was reported on Yap island, Federated States of Micronesia. A subsequent outbreak occurred in French Polynesia in 2013-2014, with more than 28,000 suspected Zika virus infections reported.

Brazil reported the first Zika case in the Americas in 2015. Since that time, the virus has spread, and outbreaks are currently occurring in many countries and territories in the Americas, including the Commonwealth of Puerto Rico and the US Virgin islands.[2]

What Are the Symptoms and Diagnosis of Zika?

About 1 in 5 people infected with Zika virus will get sick. For those who are symptomatic, symptoms are typically mild and self-resolving; for this reason, most people will not realize they have been infected.

The most common symptoms of Zika virus are fever, rash, joint pain, or conjunctivitis. Symptoms typically begin 2 -7 days after being bitten by an infected mosquito. Severe disease requiring hospitalization is uncommon. Fatalities caused by Zika virus are rare.

Zika virus usually remains in the blood of an infected person for about a week, but it can be found longer in some people. During the first week after onset of symptoms, Zika virus disease can often be diagnosed by performing reverse-transcriptase polymerase chain reaction (RT-PCR) on serum.

Currently, no vaccine or medication exists to prevent to treat Zika virus infection. There are no commercially available diagnostic tests for Zika virus disease.[4]