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 Brazil. Brazil has had the highest number of reported ZIKV cases worldwide (more than 200,000 by 24 December 2016) and the most cases associated with microcephaly and other birth defects (2,366 confirmed by 31 December 2016). 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 disease. 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.

Magnitude and frequency variations of vector-borne infection outbreaks using the Ross-Macdonald model: explaining and predicting outbreaks of dengue fever.

The classical Ross-Macdonald model is often utilized to model vector-borne infections; however, this model fails on several fronts. First, using measured (or estimated) parameters, which values are accepted from the literature, the model predicts a much greater number of cases than what is usually observed. Second, the model predicts a single large outbreak that is followed by decades of much smaller outbreaks, which is not consistent with what is observed. Usually towns or cities report a number of recurrences for many years, even when environmental changes cannot explain the disappearance of the infection between the peaks. In this paper, we continue to examine the pitfalls in modelling this class of infections, and explain that, if properly used, the Ross-Macdonald model works and can be used to understand the patterns of epidemics and even, to some extent, be used to make predictions. We model several outbreaks of dengue fever and show that the variable pattern of yearly recurrence (or its absence) can be understood and explained by a simple Ross-Macdonald model modified to take into account human movement across a range of neighbourhoods within a city. In addition, we analyse the effect of seasonal variations in the parameters that determine the number, longevity and biting behaviour of mosquitoes. Based on the size of the first outbreak, we show that it is possible to estimate the proportion of the remaining susceptible individuals and to predict the likelihood and magnitude of the eventual subsequent outbreaks. This approach is described based on actual dengue outbreaks with different recurrence patterns from some Brazilian regions.

Discovery of a new focus of human onchocerciasis in central Brazil.

An autochthonous case of human onchocerciasis was reported 13 years ago in the town of Minaçu, northern Goiás (Brazil), but a subsequent survey of the population using the traditional technique of examining skin biopsies with the light microscope failed to detect other cases. Recent surveys using more sensitive diagnostic techniques (serodiagnosis, DNA probes, Mazzotti test) that are detailed in this paper revealed the presence of other cases of the disease in Minaçu, the nearby town of Formoso and at the Buracão gold mine near Paranã. The data show that transmission of the disease has occurred to local people living in town and on farms and that gold miners (garimpeiros) are a likely source of infection.

[Preliminary activities of the program for the control and treatment of onchocerciasis in the Yanomâmi territory, Roraima, Brazil]. / Atividades preliminares do programa de controle e tratamento da oncocercose no território Yanomâmi, Roraima, Brasil.

After to characterize the clinic and epidemiological picture of the onchocerciasis in Yanomâmi region, RR, Brazil, begun in 1993, the National Health Foundation (FNS) implemented a Control and Treatment Pilot Project in Tootobi and Balawaú. Here, it was studied skin biopsies from 426 inhabitants. In the nodules of 86.7% from patients was encountered Onchocerca volvulus. The over-all prevalence in the examined population was 66.2%. The treatment with ivermectin covered 80.1% of total population. Adverse reactions, light and moderate, of the medicament were reported in 12.3% of the patients. These results agreeing with the medical literature and suggesting the viability of to increase of the programme for all Yanomâmi area in the next phase.

[Identifying areas of epidemiological stratification in an onchocerciasis focus in Yanomami territory, Roraima, Brazil]. / Identificação de áreas de estratificação epidemiológica no foco de oncocercose na região Yanomami, Roraima, Brasil.

In this paper, aimed at suitable planning, analysis, and follow-up of treatment, control, and eradication in a human onchocerciasis program, were studied 27 geographic areas and examined 3,974 inhabitants. Four epidemiological areas with different prevalences were identified and stratified.