(This video was updated on Feb. 2, 2016.) Authorities have confirmed more than 30 cases of Zika virus in the United States. Here's what you need to know. (Gillian Brockell/The Washington Post)

This post has been updated.

Florida and Illinois state officials said several of their residents who recently traveled to countries where Zika virus is found have tested positive for the virus. Texas and Hawaii have also confirmed travel-related cases.

In Illinois, the health department said their two cases involve pregnant women who traveled to countries where the mosquito-borne disease is spreading. Doctors are monitoring their health and pregnancies, according to a statement posted Tuesday on the department’s website.

Illinois officials said there is virtually no risk to other residents because people cannot contract the virus from another person, only through the bite of an infected mosquito. However, a statement from the department's director, Nirav D. Shah, warned that "since this is a time of year when people travel to warmer climates and countries where Zika virus is found, we are urging residents, especially pregnant women, to take preventive measures when traveling in affected countries and check health travel advisories."

In Florida, department spokeswoman Mara Gambineri said Wednesday that the state has three travel-related cases. None of the individuals are pregnant. Two residents of Miami-Dade county traveled to Colombia in December; a third case in Hillsborough County, where Tampa is, involves someone who traveled to Venezuela in December, she said.

While illness is usually mild, global health officials are worried about a possible link between Zika virus infection in pregnant women and subsequent birth defects.

The Centers for Disease Control and Prevention is advising obstetricians and other health-care professionals who care for pregnant women to test them for Zika infection if they show symptoms after visiting more than a dozen countries and territories where local transmission of the virus has occurred.

The interim guidelines, released Tuesday, focus on pregnant women who have fever, rash, muscle aches or conjunctivitis (pink eye) during or within two weeks of their travel to any of those locations. A positive finding for the virus should be reported to the appropriate local or state health department, CDC said.

Pregnant women who test positive should consider scheduling regular ultrasounds to monitor the growth of their fetus. Officials say that "increasingly strong evidence" points to a link between the virus and fetal brain damage.

Because no medication or vaccine is available, treatment focuses on easing symptoms. Pregnant women who have fever should be given acetaminophen.

But CDC is urging them not to visit those countries at all. The travel advisory it issued late Friday named Brazil and neighboring countries and territories throughout Latin America and the Caribbean where local transmission of Zika has occurred in recent months.

Brazil, which is experiencing an outbreak of the mosquito-borne virus, has had more than 3,500 children born with microcephaly since October. The rare condition, marked by an abnormally small head, is associated with incomplete brain development.

Hawaii health officials say a baby recently born with microcephaly at an Oahu hospital was infected with the Zika virus in utero.

In reporting the laboratory confirmation from CDC, the state health department said the child’s mother probably had a Zika infection while living in Brazil during the spring.

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