The Martha’s Vineyard Hospital has issued a health alert concerning the Zika virus, asking pregnant women who have traveled to certain countries, including Brazil, to contact doctors at the hospital.

Only one out of five people who contract the mosquito borne virus develop symptoms, which include fever, rash, joint pain, or conjunctivitis (red eyes) lasting for a few days to a week. More serious illnesses are uncommon. Doctors suspect the virus could be linked to miscarriages and severe birth defects.

The hospital health alert names Barbados, Bolivia, Brazil, Cape Verde, Colombia, Guatemala, Ecuador, El Salvador, Guadeloupe, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Samoa, St. Martin, Suriname, and Venezuela as places where outbreaks are underway.

“If you are pregnant and have traveled to any of these countries, please let Martha’s Vineyard Hospital staff know,” the alert states.

The Zika virus has been linked to babies born with severe birth defects in Brazil, where government health officials report 1.5 million people have contracted the virus.

The U.S. Centers for Disease Control and Prevention issued a travel alert on Monday, advising people traveling in affected countries to use precautions against mosquito bites, including insect repellents and treated clothing.

The World Health Organization (WHO) on Monday said the infection constitutes a public health emergency of international concern.

The disease is spread by mosquitoes, which contract the virus when they bite an infected human and spread the disease when they bite another human. The Zika virus can also spread from pregnant women to their babies during pregnancy.

There is no vaccine or medication to prevent the disease.