445. Cross-Reactivity Between Zika and Dengue Virus: A Cross-Sectional Analysis in Rio Grande do Norte, Brazil

BACKGROUND: Preexisting DENV antibodies may have a cross-reactivity against ZIKV. A recent primate study suggested that prior DENV infection does not adversely impact subsequent ZIKV disease and might be protective. This study aimed to evaluate the relation between a Dengue Fever (DF) outbreak in 2016 and the prevalence of ZIKV infection in Rio Grande do Norte (RN), a Brazilian northeast state endemic for arboviruses. METHODS: A cross-sectional analysis was conducted using data obtained through the RN Department of Health from January 2015 to April 2017. We analyzed the epidemiological behavior of DF and Zika Virus Disease in RN (last three summers). RESULTS: From January to March in 2015, 2016, and 2017, there were 6,902, 34,642, and 1,677 DF suspected cases, respectively. The number of confirmed DF cases in 2015, 2016, and 2017 were 523, 7,599, and 204, respectively. Regarding ZIKV infection, the number of suspected cases of between January to April during 2016 and 2017 were 3,486 and 86, respectively. The number of confirmed ZIKV infection in 2016 and 2017 were 97 and 0, respectively. Adding up the total cases of ZIKV infection which occurred during 2015 and 2016, we obtain a total of 14,584 (8,743 + 5,841). This number represents less than 0.5% of the RN population (3,409 million). CONCLUSION: This epidemiological evidence support our hypothesis that the DF outbreak in 2016 has contributed to the decrease of 97.53% (86/3,486) in the prevalence of ZIKV infection (suspected cases) in 2017. It may be explained by preexisting DENV antibodies might partially neutralize ZIKV infection through serologic cross-reactivity. It supports the results found on the recent primate study. In addition, our findings contradict the theory (based on in vitro experiments only) that previous immunity to DENV causes an enhancement of the immunological response in individuals exposed to ZIKV. Given the fact of the total suspected ZIKV cases in 2015 and 2016 represent less than 0.5% of the RN population, we cannot state that there are fewer Zika cases in 2017 because the population has been previously immunized. These data are highly relevant from a public health standpoint given that regions which experienced ZIKV outbreak in Brazil are endemic for DF and suggests that DENV vaccines might also offer some protection against ZIKV infection. DISCLOSURES: All authors: No reported disclosures.