“Our study was in a very small urban area, and it is likely that in other parts of Brazil, even different neighbourhoods within the same city, people are still susceptible to Zika infection,” Marques said.
Study participants gave multiple blood samples before, during and after the Zika epidemic.
Samples collected in October 2014 and March 2015 were almost entirely negative for Zika, but by October 2015, 63 per cent showed evidence of Zika infection.Before the Zika outbreak, a subset of 642 participants also had been tested for previous dengue infection, and 86 per cent were positive.
Specifically, the test assessed the level of antibodies the participants had in their blood against dengue.
The team found that each doubling of dengue antibody levels corresponded to a nine per cent reduction in risk of Zika.
“This means that there are some cross-protective antibodies that dengue provides against Zika. Future study may be warranted to assess whether the new dengue vaccines could be useful in preventing Zika infection,” said Marques.
Paradoxically, researchers at the University of Florida, revealed that participants who had a very recent dengue infection were actually more susceptible to Zika.
The scientists suspect several possible explanations: It could be that protective antibodies have not developed yet or there is something about these people’s immune systems that increases their risk of contracting Zika.The mosquitoes that transmit dengue also transmit Zika, so a recent dengue infection could simply mean they are in a place where Zika transmission is active as well, researchers said.
