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Zika Virus

Disease Information

Zika virus is spread to people primarily through mosquito bites. Two species, called Aedes aegypti and Aedes albopictus, are the only mosquitoes known to transmit the disease. Both are found in many other countries and in some parts of the United States, but not in Oregon. View a map of countries with a risk of Zika. Zika virus can also be spread to sexual partners by men or women who develop Zika symptoms after infection. We know this because Zika infections have occurred in persons who did not travel outside of the United States, but who did have sex with a returning traveler who was infected with the disease.

Four out of five people who get Zika show no signs of illness. Those who do get sick usually have fever, rash, joint pain, or irritated, red eyes. Other symptoms can include muscle pain and headache. People who do get sick typically show these symptoms from three to 14 days after getting bitten by an infected mosquito or having sex with an infected person. Severe disease is uncommon, and hospitalization is rare. However, Zika infection in the mother during pregnancy is associated with health problems in babies.

The spring 2015 Zika virus outbreak in Brazil was the first in the Western Hemisphere, and the outbreak has since spread to other countries in the Americas as well as to some areas of the United States. Zika virus infections have been confirmed in travelers returning from Zika-affected regions. Zika infections have also been identified in non-traveling sex partners of men and women who got Zika during travel in Zika-affected regions. For people traveling to areas where Zika is spread by mosquitoes, avoiding mosquito bites and avoiding unprotected sex with potentially infected partners are the best ways to prevent infection. To avoid spreading Zika virus to pregnant women, men or women returning to the United States from Zika outbreak regions should avoid sex, or use a condom during any sexual activity with pregnant partners for the duration of the pregnancy.

Zika virus and pregnancy

Zika virus infection during pregnancy might increase the risk of losing the pregnancy. Some babies whose mothers had contracted Zika virus during pregnancy were born with fetal abnormalities, including unusually small heads (“microcephaly”) and problems with brain development. CDC recommends that pregnant women not travel to areas affected by Zika virus. CDC has issued guidance for pregnant women returning from travel to a region where the virus is spread by mosquitoes, and guidance for prevention of sexual transmission.


There is no vaccine to prevent Zika virus disease. Virus transmission can be prevented by avoiding mosquito bites and by avoiding unprotected sex with men or women who traveled to a Zika-affected region.

CDC has resources on easy ways to avoid bug bites.

Men and women who traveled to Zika-affected areas and who have a pregnant partner should take special precautions. The CDC recommends that they not have sex or that they use condoms during sex for the duration of the pregnancy.

Travelers infected with Zika could be bitten by mosquitoes after returning to the U.S. The types of mosquitoes known to carry Zika infection do not live in Oregon but we are monitoring mosquito populations in Oregon to make sure none move here. Nonetheless, we don’t want to find out the hard way that local mosquitoes can transmit the disease as well. Therefore, people returning to Oregon with potential Zika virus infection, or other mosquito-borne diseases, for that matter, should take care to protect themselves against mosquito bites for three weeks after returning.

If you have any concerns about Zika virus, please talk to your healthcare provider.

Disease Reporting

For Healthcare Providers

In Oregon, Zika is considered an infection that is typically "arthropod vector-borne" and should be reported to your local health department within one public health authority working day.

Also, please see our special webpage: Zika information for healthcare providers. It includes information about testing criteria, how to report cases, guidance on specimen collection, clinical management and more.

For Local Health Departments

Local health departments should report all cases to the Oregon Public Health Division (OPHD). The OPHD needs to pre-approve testing at OSPHL.

Local health departments should ensure that an OSPHL Virology/Immunology test request form and the CDC Specimen Submission Form are filled out by the treating physician or the local health department and appropriate sample is submitted for testing. Local health departments may direct the treating physician or clinical laboratory to the CDC Instructions for Submitting Specimens.

For Clinical Labs

Zika virus is an infection that is typically “arthropod vector-borne” so laboratories are required to report Zika virus infection to the local public health department within one local public health authority working day. Physicians desiring testing for Zika virus must first report cases to the local health department, which will discuss appropriateness of testing and type of testing most appropriate for the clinical situation.

See Also

CDC Factsheet 

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