O bairro de Pau da Lima, em Salvador, foi a localidade escolhida para a pesquisa / Foto: Divulgação ISC-UFBA

People who have acquired immunity after dengue virus infection have a reduced risk of Zika virus (ZIKV) transmission. This is what a research conducted by the Institute of Collective Health of the Federal University of Bahia (UFBA) and published in Science, one of the most prestigious academic journals in the world. The study was done in collaboration with Fiocruz Bahia and other international partners, such as the Yale University School of Public Health in the United States.

The researchers followed 1,453 residents of the Pau da Lima neighborhood in Salvador between March and October 2015. The data show that around 73% of the people surveyed in the locality contracted Zika during the outbreak period. But there was a 25% reduction in contagion among those who developed antibodies after a previous dengue infection. In some subgroups, this percentage reached 44% in the reduction index. The study is the first to evaluate and demonstrate that dengue immunity can protect against a Zika infection in human populations.

The work was coordinated in Bahia by Professor Federico Costa and was attended by PhD student Nivison Nery Jr, both from the UFBA Institute of Collective Health. To achieve the result, they used a new test to identify Zika infections in large populations. According to the researchers, Zika and dengue viruses share many genetic similarities and usually circulate in the same regions.

The research also suggests that there was immunity in the population infected by the Zika virus itself, which explains the reduction of transmission and the rapid decline of the outbreak in the locality. “The Zika pandemic has generated high overall immunity rates to this virus in the Americas, which will be a barrier to outbreaks in the coming years,” said Professor Federico Costa. He also considers that a joint study of zika and dengue viruses can help to understand the impact of vaccines, such as dengue, and other health actions to combat these diseases.