Zika virus – Incidence and trends
To date, 35 countries and territories have confirmed local, vector-borne transmission of Zika virus in the Region of the Americas since 2015 (Figure 1). Since the last Pan American Health Organization/ World Health Organization (PAHO/WHO) Zika Epidemiological Update on 21 April, no new countries or territories hav e confirmed vector-borne autochthonous transmission of Zika virus.
Suspected and confirmed Zika virus cases have been showing a downward trend in some countries in the Americas, consistent with trends that have been observed in corresponding periods in previous years for other mosquito-borne diseases. Conversely, the trend of cases is still increasing in countries and territories in the Americas for which the outbreak started later, such as the Dominican Republic and Guadeloupe which are highlighted below.
In Brazil, report of Zika cases has been mandatory since February 2016 and as of epidemiological week (EW) 13 of 2016, a total of 91,387 probable Zika cases were recorded at national level (incidence rate of 44.7 cases per 100,000 population ). The southeast region reported the highest number of accumulative probable cases (35,505) which may due to the more recent start of the outbreak in the states of that region. The region reporting the second highest number of probable cases (30,286) is the Northeast. The highest incidence rate is reported by the Center-West region (113.4 /100,000) followed by the Northeast (53.5 cases/100,000). In addition, three deaths linked to Zika virus were confirmed in São Luis (Maranhão State), Benevides (Pará State), and Serrinha (Rio Grande do Norte State), as reported previously. See full report.
Illustrated below is the decreasing trend of reported cases of Zika virus in El Salvador and Jamaica, countries and territories whose outbreaks began in 2015. In contrast, the increasing trend in the number of suspected cases of Zika virus for countries and territories whose outbreaks began in 2016, the Dominican Republic and Guadeloupe, is illustrated below.
El Salvador
Since the beginning of the outbreak in November 2015 through the end of 2015, suspected Zika virus cases had increased in El Salvador, followed by a decreasing trend until EW 12 of 2016. A slight increase is observed between EW 12 and EW 13; this may be attributed to underreporting during Easter holidays which occurred during EW 12. This trend is similar to the one observed in Martinique and described in the Zika Epidemiological Update on 21 April. This epidemiological curve is subject to change as cases are retroactively reported.
Jamaica
Similarly, Jamaica the number of suspected Zika virus cases is decreasing in Jamaica after an increase observed since the initial reports of Zika virus in EW 39 of 2015. The highest number of suspected cases was recorded in EW 5 of 2016, followed by a decreasing trend of suspected cases through EW 14.
Dominican Republic
Since the beginning of the outbreak in EW 49 of 2015 to EW 15 in 2016, an increasing trend of suspected and confirmed Zika virus cases is observed in the Dominican Republic. A decrease in cases was reported in EW 12, but may be attributed to underreporting of Zika virus during the Easter holidays. In EW 15, the highest number of Zika virus cases was recorded. Similarly an increasing trend is observed with the rash febrile illness data collected by the Dominican Republic in correlation with the period starting from EW 1 through EW 15 of 2016.
Guadeloupe In Guadeloupe, since the first reports of Zika virus cases in EW 2 of 2016, the trend of Zika virus cases has steadily increased. The temporary decrease of cases observed between EW 10 and EW 12 of 2016 is similar to that observed in El Salvador and the Dominican Republic.