A cocktail of three antibodies has shown promise in preventing Zika virus infection in monkeys, and moves next into trials in humans, researchers said Wednesday.

The mosquito-borne Zika virus swept across Latin America, the Caribbean and southern United States in 2015 and 2016, sparking a global health emergency due to its ability to cause brain-related birth defects.

While the threat posed by Zika has subsided somewhat because people cannot become infected twice, researchers are pressing on with attempts to develop the first vaccine to prevent Zika infection and its most dangerous complication, microcephaly in fetuses and babies.

"This is a promising intervention to prevent and treat Zika virus infection during pregnancy," said David Watkins, a professor at the University of Miami's Miller School of Medicine.

"We would like to develop this antibody combination and get it into clinical trials as soon as possible."

Researchers identified three potent antibodies called SMZAb1, SMZAb2 and SMZAb5, isolated from a South American patient.

"We administered a cocktail of these three antibodies to nonhuman primates one day before challenging them with Zika virus that had been isolated from a pregnant woman during the 2016 epidemic in Rio de Janeiro," said Watkins.

"To our surprise, this prophylactic treatment completely prevented the virus from taking hold in the animals."

Researchers found no measurable virus levels in the blood of the four animals treated with the monoclonal combination, and no immune system response, indicating the virus had been blocked completely, said the report in the journal Science Translational Medicine.

Four monkeys that were not given the antibodies before being exposed to Zika became ill with the virus for seven days.

"Since these antibodies have exceptional safety profiles in humans and cross the placenta, this combination could be rapidly developed to protect uninfected pregnant women and their fetuses," Watkins said.