Zika virus, first identified in Uganda in 1947, is transmitted by the same type of mosquito that carries dengue fever, yellow fever, and chikungunya virus. A mosquito bites an infected person and then passes those viruses to other people it bites. Outbreaks did not occur outside of Africa until 2007, when it spread to the South Pacific.
The CDC has confirmed Zika can spread through sex, usually after a person traveled to an area where Zika has broken out, got the virus, and gave the virus to a sex partner who did not travel. Infected women and men can both pass the virus to sex partners — even if they haven’t shown symptoms of infection, the CDC says.
The CDC is aware of a report that Brazilian scientists have found the virus in the saliva and urine of infected people, CDC Director Tom Frieden, MD, told reporters, but more information is needed.
What are the symptoms of Zika virus?
The disease can cause fever, rash, joint pain, and redness in the whites of the eye. But most people won’t know they have it.
“Only about 1 in 5 people with the virus will exhibit symptoms,” says Amesh Adalja, MD, a spokesman for the Infectious Diseases Society of America. “The vast majority have no symptoms at all.”
Zika has “never been thought of as a severe infectious disease until now,” Adalja says.
Is Zika similar to other mosquito-borne illnesses, such as dengue fever, chikungunya, or West Nile virus?
All can cause a variety of flu-like symptoms that range in severity and can last from a few days to more than a week. As with Zika, few people infected with dengue or West Nile will show any symptoms.