Spatiotemporal transmission dynamics of co-circulating dengue, Zika, and chikungunya viruses in Fortaleza, Brazil: 2011-2017

The mosquito-borne viruses dengue (DENV), Zika (ZIKV), and chikungunya (CHIKV), now co-endemic in the Americas, pose growing threats to health worldwide. However, it remains unclear whether there exist interactions between these viruses that could shape their epidemiology. This study advances knowledge by assessing the transmission dynamics of co-circulating DENV, ZIKV, and CHIKV in the city of Fortaleza, Brazil. Spatiotemporal transmission dynamics of DENV, ZIKV, and CHIKV were analyzed using georeferenced data on over 210,000 reported cases from 2011 to 2017 in Fortaleza, Brazil. Local spatial clustering tests and space-time scan statistics were used to compare transmission dynamics across all years. The transmission of co-circulating viruses in 2016 and 2017 was evaluated at fine spatial and temporal scales using a measure of spatiotemporal dependence, the τ-statistic. Results revealed differences in the diffusion of CHIKV compared to previous DENV epidemics and spatially distinct transmission of DENV/ZIKV and CHIKV during the period of their co-circulation. Significant spatial clustering of viruses of the same type was observed within 14-day time intervals at distances of up to 6.8 km (p<0.05). These results suggest that arbovirus risk is not uniformly distributed within cities during co-circulation. Findings may guide outbreak preparedness and response efforts by highlighting the clustered nature of transmission of co-circulating arboviruses at the neighborhood level. The potential for competitive interactions between the arboviruses should be further investigated.

Tendência secular da peste no Estado do Ceará, Brasil

Após a sua introdução no Ceará, Brasil, em 1900, a peste focalizou-se em sete complexos ecológicos: Chapada do Araripe e Serras da Ibiapaba, do Baturité, do Machado, das Matas, da Pedra Branca e de Uruburetama. As atividades de vigilância nesses focos no período de 1935/2004 foram desenvolvidas sucessivamente pelo Departamento Nacional de Saúde, Serviço Nacional de Peste, Departamento Nacional de Endemias Rurais, Superintendência de Campanhas de Saúde Pública, Fundação Nacional de Saúde e finalmente pela Secretaria de Vigilância em Saúde. A análise dos dados levantados sobre a ocorrência de casos humanos nesses 70 anos permite identificar diferentes padrões de circulação da enfermidade na população humana, caracterizados pela alternância de momentos de elevadas incidências e de silêncio, possibilitando estabelecer uma periodização cronológica com características epidemiológicas próprias. Conclui-se desses resultados que a peste ainda deve ser considerada uma ameaça potencial, o que justifica revitalizar as ações de vigilância epidemiológica, o que só ocorrerá com o fortalecimento de todas as instâncias do Sistema Único de Saúde.