What Is Zika?

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The Zika virus spreads to people primarily through the bite of an infected Aedes species mosquito, and a person with Zika can pass it to his or her sex partners.  Zika is affecting parts of Central and South America, Mexico, the Caribbean, the United States and other places listed by the Centers for Disease Control and Prevention. Zika virus can cause serious birth defects in babies born to women who were infected while pregnant. However, not all women infected with Zika during pregnancy have poor pregnancy outcomes. Some pregnant women and their infants in Chicago have tested positive for Zika; all cases are travel associated. No local transmission of Zika has occurred in Chicago.

Though the mosquitos currently infected with Zika are not native to the Chicago area, there are simple steps you can take to better protect yourself both at home and when traveling to parts of the world where Zika virus is more common.

 
 
 

How Is Zika Transmitted?


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Through mosquito bites

ZIKA VIRUS IS TRANSMITTED TO PEOPLE PRIMARILY THROUGH THE BITE OF AN INFECTED AEDES SPECIES MOSQUITO (A. AEGYPTI AND A. ALBOPICTUS). THESE ARE THE SAME MOSQUITOES THAT SPREAD DENGUE AND CHIKUNGUNYA VIRUSES.

These mosquitoes typically lay eggs in and near standing water in things like buckets, bowls, animal dishes, flower pots and vases. They prefer to bite people, and live indoors and outdoors near people. Mosquitoes that spread chikungunya, dengue, and Zika are aggressive daytime biters, but they can also bite at night.

Mosquitoes become infected when they feed on a person already infected with the virus. Infected mosquitoes can then spread the virus to other people through bites.

The Chicago Department of Public Health conducts surveillance to identify the presence of Aedes mosquitoes in Chicago and target mosquito control. In 2016, Aedes albopictus were collected around a single tire recycling facility. Targeted spraying and tire removal were effective in eliminating mosquitoes in that area.  Surveillance for Aedes mosquitoes will continue in 2017.


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From mother to child

A pregnant woman can pass Zika virus to her fetus during pregnancy. Zika is a cause of microcephaly and other severe fetal defects. Microcephaly is a birth defect in which a baby’s head is smaller than expected when compared to babies of the same sex and age. Babies with microcephaly often have smaller brains that might not have developed properly.  Microcephaly is not the only birth defect associated with Zika infection.  Scientists are studying how Zika virus affects mothers and their children to better understand the full range of potential health problems that Zika virus infection during pregnancy may cause. 

A pregnant woman already infected with Zika virus can pass the virus to her fetus during the pregnancy or around the time of birth.

TO DATE, THERE ARE NO REPORTS OF INFANTS GETTING ZIKA VIRUS THROUGH BREASTFEEDING. BECAUSE OF THE BENEFITS OF BREASTFEEDING, MOTHERS ARE ENCOURAGED TO BREASTFEED EVEN IN AREAS WITH RISK OF ZIKA. 


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Through sex

Zika can be passed through sex from a person who has Zika to his or her partners,  even if the infected person does not have symptoms at the time. Learn how to protect yourself during sex. Zika can be passed from a person without symptoms, before their symptoms start, while they have symptoms, and after their symptoms end. Four out of five people infected with Zika won’t have symptoms.

Studies are underway to find out how long Zika stays in the semen and vaginal fluids of people who have Zika, and how long it can be passed to sex partners. We know that Zika can remain in semen longer than in other body fluids, including vaginal fluids, urine, and blood. CDC recommends using condoms after travel to Zika affected areas. Condoms should be used for at least 8 weeks after last exposure or symptom onset for women and at least 6 months after last exposure or symptom onset for men before trying to conceive.  Condoms should be used throughout pregnancy if potential exposure has occurred for either partner.


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Through blood transfusion

To date, there have not been any confirmed blood transfusion transmission cases in the United States.  Blood centers perform blood and donor screening to reduce the risk for transfusion-transmitted Zika virus. All donor blood in Illinois is tested for Zika.