Establishment and cryptic transmission of Zika virus in Brazil and the Americas

Transmission of Zika virus (ZIKV) in the Americas was first confirmed in May 2015 in northeast Brazil1. Brazil has had the highest number of reported ZIKV cases worldwide (more than 200,000 by 24 December 20162) and the most cases associated with microcephaly and other birth defects (2,366 confirmed by 31 December 20162). Since the initial detection of ZIKV in Brazil, more than 45 countries in the Americas have reported local ZIKV transmission, with 24 of these reporting severe ZIKV-associated disease3. However, the origin and epidemic history of ZIKV in Brazil and the Americas remain poorly understood, despite the value of this information for interpreting observed trends in reported microcephaly. Here we address this issue by generating 54 complete or partial ZIKV genomes, mostly from Brazil, and reporting data generated by a mobile genomics laboratory that travelled across northeast Brazil in 2016. One sequence represents the earliest confirmed ZIKV infection in Brazil. Analyses of viral genomes with ecological and epidemiological data yield an estimate that ZIKV was present in northeast Brazil by February 2014 and is likely to have disseminated from there, nationally and internationally, before the first detection of ZIKV in the Americas. Estimated dates for the international spread of ZIKV from Brazil indicate the duration of pre-detection cryptic transmission in recipient regions. The role of northeast Brazil in the establishment of ZIKV in the Americas is further supported by geographic analysis of ZIKV transmission potential and by estimates of the basic reproduction number of the virus

Nightly patterns of calling activity in anuran assemblages of the Cerrado, Brazil

Anurans living in species-rich assemblages may experience acoustic niche overlap. To deal with potential masking interference during reproductive activity, species can present acoustic partitioning based on differences in calling period. Studies addressing this question in tropical assemblages have mainly focused on the seasonal scale, and little is known about nightly variation in calling. Here, we reported on phenology and abundance of five tropical anuran assemblages at both seasonal and daily scale and tested the effects of temperature and relative humidity on calling activity patterns of 19 species. Based on 420 hourly acoustic surveys, an overall peak of calling activity in between the first and fourth hour after sunset was identified by Rayleigh’s circular test, with a gradual decrease until sunrise. This nightly pattern was followed by most of the species in the assemblages and similarly observed for species presence and abundance of calling males. The acoustic niche overlap was greater than expected by chance within the assemblages, while no pattern of coincidence or segregation was found for the syntopic congeneric species (Dendropsophus, Boana and Leptodactylus). Moreover, the calling activity of the assemblages, measured as richness and diversity of calling species, was negatively influenced by air and water temperature and positively by relative humidity. Thus, climatic variables act as driver factors to determine calling activity and reproduction of anurans at daily scale. The absence of a segregation pattern at the assembly or genus levels in the calling activity over time indicates that the use of the acoustic temporal niche is not a limiting resource for Cerrado anurans.VG would like to thank the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brazil (CAPES) for doctoral fellowship, and RPB thanks the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq 308204/2013-1) for research productivity fellowship. VG was supported by CAPES/PROCAD-AM 1701/2018 (Grant No. 88887.374100/2019-00). DL was supported by a Global Marie S. Curie Fellowship (EAVESTROP-661408) granted by the European Commission (Program H2020) and a post-doctoral grant (2016-T2/AMB-1722, Atracción de Talento Investigador, Spain) provided by the Comunidad de Madrid and acknowledges a research project (CGL2017-88764-R, MINECO/AEI/FEDER, Spain) by the Ministerio de Economía, Industria y Competitividad. This paper is developed in the context of National Institutes for Science and Technology (INCT) in Ecology, Evolution and Biodiversity Conservation, supported by MCTIC/CNPq (Proc. 465610/2014-5) and FAPEG (Proc. 201810267000023)