University of Hawaii researchers say severe birth defects related to the Zika virus occurred in the islands several years before this year’s outbreaks in Brazil and Puerto Rico.

UH scientists discovered a prevalence of Zika-­related antibodies in Hawaii mothers who delivered babies between 2009 and 2012, linking the infection and a condition known as microcephaly, a rare birth defect that causes brain damage and is characterized by an infant’s abnormally small head.

Researchers identified six mothers who gave birth to babies with microcephaly using blood samples collected from mothers at Kapiolani Medical Center for Women &Children. The samples had been stored at UH for future research. Zika virus antibodies were detected in three of the six mothers who delivered babies with birth defects.

“We knew that the virus was in the Pacific since 2007, and we knew that there was something going on here, but we didn’t have any evidence,” said Dr. Vivek Nerurkar, chairman of the UH John A. Burns School of Medicine’s Department of Tropical Medicine, Medical Microbiology and Pharmacology. “We had a suspicion, so when the 2016 outbreak happened in Brazil and then in Puerto Rico, we started looking. All the mothers delivered babies at Kapiolani, but nobody noticed it.”

Nerurkar and his colleagues first found microcephaly associated with the Zika virus in a baby born in Hawaii in 2015 to a mother who had traveled to Brazil. In recent years there have also been Zika outbreaks in Micronesia and French Polynesia.

There are no vaccines or medications for Zika, which is spread mostly by infected mosquitoes and passed from a pregnant woman to her fetus, as well as through sexual transmission.

“We need to be more proactive in tracking pregnant women and testing for the (virus) ahead of time before birth,” Nerurkar said. “It may be time for health care professionals to routinely caution newly pregnant mothers or those planning to become pregnant about (Zika), and offer prenatal tests to detect for the presence of the virus. Ideally, families can plan for safe pregnancies by avoiding travel to areas of known outbreaks.”

The list of current outbreaks includes some Caribbean and Pacific islands. Hawaii has not had an outbreak or reported transmission of the virus locally.

Nerurkar leads a team of scientists working to develop a Zika vaccine as well as a better way to quickly detect the disease.