In the Region of the Americas, between epidemiological week (EW) 1 and EW 49 of 2021, a total of 1,324,108 cases1 of arboviral diseases were reported. Of those, 1,173,674 (89%) were dengue cases, 131,630 were chikungunya cases, and 18,804 were Zika cases.
Figure 1 shows the circulation pattern of dengue, chikungunya and Zika in the last 14 years. Since 2014, the impact of the introduction of chikungunya (December 2013) is observed. Similarly, after the introduction of the Zika in 2015, there was a widespread circulation of the virus in 2016. However, the circulation of dengue has continued to predominate.
Figure 1. Distribution of reported cases of dengue, chikungunya, and Zika by year of report. Region of the Americas, 2008-2021 (up to EW 494 of 2021).
In the Region of the Americas, the total number of cases of arboviral disease reported in 2021 as of EW 49 (1,324,108 cases) represents approximately a 45% relative decrease compared to the same period in 2020 (2,408,928 cases). In 2021, as of EW 49, in the Region of the Americas, during the first semester of 2021 an upward trend is observed in cases of dengue, chikungunya, and Zika, which reached their peak in EW 14, EW 22 and EW 26, respectively (Figures 2-4).
In the Region of the Americas, dengue is the arbovirus that causes the highest number of cases, with epidemics that occur cyclically every 3 to 5 years. In 2019, the highest number of dengue cases occurred in the Region of the Americas; more than 3.1 million cases were reported, including 28,203 severe dengue cases and 1,773 deaths. Additionally, the simultaneous circulation of other arboviruses, such as chikungunya and Zika, both transmitted by the same vector, Aedes aegypti, which is present in almost all the countries and territories of the Region of the Americas.
Since 2020, the circulation of the dengue virus and other arboviruses has been occurring simultaneously with the active transmission of the SARS-CoV-2 virus in endemic countries and territories in the Region of the Americas. Meanwhile, new variants of concern of SARS-CoV-2 are detected and inadequate coverage of the vaccine against COVID-19, in endemic areas of these arboviruses where the public health and social measures to prevent COVID-19 are relaxing, pose a complex epidemiological situation, a high demand in health services, as well as a constant challenge for health systems in all its components and levels, including epidemiological surveillance.
Additionally, in December, several countries in the Region could experience an increases in precipitation, which, depending on its magnitude and impact in the endemic areas of the aforementioned arboviruses, could constitute an additional burden of arbovirus diseases for health systems in affected areas. The following is the epidemiological situation of dengue, chikungunya, and Zika in the Region of the Americas.