Yellow fever outbreak in a rural-urban mixed community of Espírito Santo, Brazil: epidemiological aspects

Abstract

Objective. To describe the epidemiological aspects of an outbreak of yellow fever (YF) that occurred in the state of Espírito Santo, Brazil, from 1 January 2017 – 31 July 2017. Methods. A descriptive, quantitative, retrospective approach analyzed secondary data obtained from the national notification systems, Information System of Diseases Notifications (SINAN), Laboratory Environment Manager (GAL), and the Espírito Santo Health Secretariat (SESA). Results. From 1 January 2017 – 8 July 2017, a total of 824 cases were reported in Espírito Santo, 307 (37%) of which were confirmed as YF. Of these, 95 (30.9%) died from the disease. Men were those most affected, corresponding to 244 (79.5%) cases, and women to 63 (20.5%) cases. The greatest incidence rate registered was in the city of Santa Leopoldina (380.2 cases/100 000 inhabitants). The outbreak evolved rapidly and a response was possible due to a multidisciplinary group created specifically to tackle the YF outbreak. Conclusions. The data were received and analyzed quickly and the response, consisting of immediate treatment of the cases and a blocking vaccination strategy, was developed to halt the progression of this fatal disease. In spite of these efforts, the case fatality rate of yellow fever remained high.

Survey on Non-Human Primates and Mosquitoes Does not Provide Evidences of Spillover/Spillback between the Urban and Sylvatic Cycles of Yellow Fever and Zika Viruses Following Severe Outbreaks in Southeast Brazil

“…Indeed, all vectors found infected herein and for previous authors were sylvatic species [34,42]. This finding, together with epidemiological, genetic and entomological records obtained during the outbreak [34,[42][43][44][45][46], reinforced the sylvatic nature of the outbreak and the absence of spillover. Briefly, the demographic characteristics of the infected humans [43,46] and the spread rates of YFV over time and space and the genetic clades found in phylogeographic analyses were consistent with an NHP-sylvatic mosquitoes-human transmission [3,44,45,47,48].…”

“…This finding, together with epidemiological, genetic and entomological records obtained during the outbreak [34,[42][43][44][45][46], reinforced the sylvatic nature of the outbreak and the absence of spillover. Briefly, the demographic characteristics of the infected humans [43,46] and the spread rates of YFV over time and space and the genetic clades found in phylogeographic analyses were consistent with an NHP-sylvatic mosquitoes-human transmission [3,44,45,47,48]. Furthermore, all investigated cases also shared ecological conditions indicating their sylvatic origin, such as contact with forested areas, including people that entered into the jungle or live in the interface between cities and the natural environment [3,49,50].…”

Difusão espaço-temporal da febre amarela silvestre em um estado do Sudeste do Brasil, 2017

“…O período sazonal da doença amarílica inicia-se em dezembro do ano anterior (SE 49 a SE 52) e se estende até maio do ano seguinte (SE 1 a SE 22) 15,16,17 . O surto teve início em dezembro de 2016 e se estendeu, pelo menos, até maio de 2017, coincidindo com a sazonalidade historicamente observada 16,17,21,22 . O mês de janeiro concentrou o maior número de casos suspeitos e confirmados de febre amarela, especialmente nos estados mais afetados, compreendidos por Minas Gerais e Espírito Santo 16,22,23 .…”

Review of data and knowledge gaps regarding yellow fever vaccine-induced immunity and duration of protection

“…Infection in humans can produce a hemorrhagic fever and is fatal in 30-60% of persons with severe disease 1,2 . Recent decades have witnessed an unprecedented emergence of YF virus activity, including in highly urbanized areas where vaccination coverage was low [3][4][5] . It has been recently estimated that roughly 400 million individuals require vaccination within at-risk zones to potentially prevent epidemic of the disease though many more might be at risk due to the recent expansion of risk zones, particularly in Brazil 3,6 YF vaccine was first developed in the 1930s after successful attenuation of the Asibi strain of YF virus to generate the strain 17D 7 .…”