The outbreak of the mosquito-borne Zika–pronounced ZEE-kah–virus has been declared a global emergency by the U.N.’s World Health Organization.

Prior to 2015, major outbreaks of Zika occurred in areas of Africa, Southeast Asia and the Pacific Islands, but more recently, a big outbreak has hit Brazil.

It’s believed that the most vulnerable to Zika are pregnant women. Officials suspect there’s a link between pregnant women catching the virus and babies being born with a neurological condition known as microcephaly, which causes a baby’s head and, in many cases, brain to be abnormally small.

1. What is the virus, and how do you catch it?

The Zika virus is a pathogen that can be transmitted through a mosquito bite. As of now, a person needs to be exposed to a mosquito that is carrying the virus in order to be infected with it. That said, health officials say a patient in Texas was infected after having sexual contact with an ill person who returned from a country where Zika was present.

The World Health Organization declared a global emergency Monday over the spread of the virus, whose current epicenter is Brazil but is circulating in many countries and territories across the Americas.

2. What is the Illinois connection?

So far, the Illinois Department of Public Health has reported three cases of Zika virus in Illinois in people who have returned from travel in places where Zika is circulating.

Two pregnant women tested positive for the virus after traveling in Honduras and Haiti, as did a man who traveled to South America.

3. How can we protect ourselves against it?

“Anyone who is traveling to countries where the Zika virus is circulating needs to take necessary precautions to prevent mosquito bites,” said Michael Angarone, assistant professor of medicine in infectious diseases at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician.

The U.S. Centers for Disease Control and Prevention has advised pregnant women to postpone travel to Brazil and other countries and regions with Zika outbreaks.

4. Are the mosquitos that can transmit the virus found here in the U.S.?

Yes. Aedes albopictus, the Asian tiger mosquito, and Aedes aegypti, the yellow fever mosquito, are both found in the U.S.

Taken together, “there are many parts of the United States that are vulnerable because of where the mosquito populations are,” Laura Harrington, chair of Cornell University’s entomology department, told the Tribune.

But so far, there have been no cases of local Zika transmission in the U.S.

5. What are the symptoms of the Zika virus?

People infected with the Zika virus may experience a fever, a rash, joint pain and red, irritated eyes. These symptoms could last for a few days or up to week and will usually occur within a few days of becoming infected.

These symptoms may sound very similar to ones associated with other, more common viruses that are circulating this time of year, like the flu, but there is no need to assume you’re infected with the Zika virus, Angarone said.

“As far as we know right now, it’s only affecting people who have traveled where it’s circulating, like Central and South America,” Angarone said. “If you have only stayed locally, it’s highly unlikely you’d have a Zika infection.”

Doctor’s advice: If you’ve traveled to a country where there have been Zika transmissions and develop a fever within 1-2 weeks of your return, Angarone suggests you visit a doctor.