Abstract Background: Zika virus (ZIKV) is a mosquito-borne virus that is also transmitted sexually, however, the epidemiological relevance of ZIKV sexual transmission in endemic regions is unclear. Methods: We performed a household-based serosurvey in Northeast Brazil to evaluate the differential exposure to ZIKV and chikungunya virus (CHIKV) among households. Individuals who participated in our previous arboviral disease cohort (indexes) were re-contacted and enrolled, and their household members were newly enrolled. Results: The Relative Risk (RR) of sexual partners being ZIKV seropositive when living with a ZIKV-seropositive index participant was significantly higher, while this was not observed among non-sexual partners of the index. For CHIKV, both sexual and non-sexual partner household members living with a CHIKV-seropositive index had a significantly higher risk of being seropositive. In the non-index based dyadic and generalized linear mixed model analyses, the odds of sexual dyads having a concordant ZIKV PRNT result was significantly higher. We have also analyzed retrospective clinical data according to the participants' exposure to ZIKV and CHIKV. Conclusion: Our data suggest that ZIKV sexual transmission may be a key factor for the high ZIKV seroprevalence among households in endemic areas and raises important questions about differential disease from the two modes of transmission. Keywords: Zika; arbovirus; chikungunya; epidemiology; mosquito; sexual transmission.

3rd November 2020 • comment

The global spread of 2019-nCoV: a molecular evolutionary analysis

by Domenico Benvenuto, Marta Giovanetti, Marco Salemi, Mattia Prosperi, Cecilia De Flora, Luiz Carlos J

The global spread of the 2019-nCoV is continuing and is fast moving, as indicated by the WHO raising the risk assessment to high. In this article, we provide a preliminary phylodynamic and phylogeographic analysis of this new virus. A Maximum Clade Credibility tree has been built using the 29 available whole genome sequences of 2019-nCoV and two whole genome sequences that are highly similar sequences from Bat SARS-like Coronavirus available in GeneBank. We are able to clarify the mechanism of transmission among the countries which have provided the 2019-nCoV sequence isolates from their patients. The Bayesian phylogeographic reconstruction shows that the 2019–2020 nCoV most probably originated from the Bat SARS-like Coronavirus circulating in the Rhinolophus bat family. In agreement with epidemiological observations, the most likely geographic origin of the new outbreak was the city of Wuhan, China, where 2019-nCoV time of the most recent common ancestor emerged, according to molecular clock analysis, around November 25th, 2019. These results, together with previously recorded epidemics, suggest a recurring pattern of periodical epizootic outbreaks due to Betacoronavirus. Moreover, our study describes the same population genetic dynamic underlying the SARS 2003 epidemic, and suggests the urgent need for the development of effective molecular surveillance strategies of Betacoronavirus among animals and Rhinolophus of the bat family.

27th February 2020 • comment