The Zika virus has made its way to the United States, with 36 people currently diagnosed with the disease. Four of the 36 are pregnant women, with the risk factor being the highest for them.

ABC News reports that the cases of Zika virus in the U.S. are spread throughout 11 states and Washington. D.C. All those infected contracted Zika virus outside of the U.S.

#ZikaVirus cases in the U.S. that the CDC is aware of so far: pic.twitter.com/ACwoRMAYd0

— TODAY (@TODAYshow) January 29, 2016

A woman in Hawaii–not counted among the 36 aforementioned sufferers of Zika virus–is believed to have had the disease. Her baby was recently born with microcephaly. This is characterized by an abnormally small head and brain, which typically leads to developmental delays. This birth defect has been associated with Zika virus in Brazil, where more than 4,000 children have been diagnosed with the condition.

Hospital in Brazil treating 130 babies with microcephaly after moms were infected with Zika https://t.co/aJRJTpiTF4 pic.twitter.com/ol56CPFkx5

— ABC News (@ABC) January 29, 2016

Researchers believe the Zika virus came to the Western Hemisphere from French Polynesia. It was first confirmed in Brazil in May.

View an interactive map that shows how the #ZikaVirus made its way to the U.S. https://t.co/e5n1cw8FhR —@Dina_Maron, graphics by @unamandita

— Scientific American (@sciam) January 27, 2016

Dr. Peter Armbruster is a professor of biology at Georgetown University.

“It is very likely an infected traveler from French Polynesia that traveled to Brazil was likely the source of the Brazilian invasion,” he tells ABC News. “Whether it is someone associated with the [World Cup], we do not know for sure.”

The U.S. Centers for Disease Control and Prevention are urging pregnant women not to travel to countries where the Zika virus transmission is ongoing. Those countries include Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela, Puerto Rico, U.S. Virgin Islands, Dominican Republic, Barbados, Bolivia, Ecuador, Guadeloupe, Saint Martin, Guyana, Cape Verde, and Samoa.