Chikungunya and Dengue Viruses Co-Circulate In the Americas

The sudden multi-year increase of chikungunya (CHIKV) and dengue cases in the Federative Republic of Brazil has raised concerns about the impact of arbovirus outbreaks on public health throughout the Region of the Americas.

As of November 21, 2024, the Pan American Health Organization (PAHO) had reported 412,089 chikungunya cases this year, 411,548 cases in 2023, and 273,841 in 2022.

Seperately, the PAHO has reported 12,522,878 dengue cases and 7,598 related fatalities in 2024.

A recent study published by BMC Medicine has revealed where these mosquito-transmitted diseases are most prevalent.

The data from CHIKV tests indicated that Brazil's Northeast region had the highest regional positivity rate in 2022 (58.1%). However, in 2023, the Southeast region recorded the highest positivity rate (40.5%).

During the first thirty epidemiological weeks of 2023 in Minas Gerais, a Brazilian state with 20 million residents, there was a 5.8-fold increase in CHIKV cases and a 3.5-fold increase in dengue compared to the same period in 2022.

All CHIKV clades are closely related to genomes from previous Brazilian outbreaks in the Northeast.

In 2024, different importation and local transmission events of two different genotypes were identified: CHIKV-Asian in the North region and ECSA in the Northeast region of Brazil. All sequenced genomes were classified as ECSA genotype. The dated phylogenetic analysis showed the presence of three main CHIKV clusters. 

Furthermore, these researchers detected the RNA of both viruses in approximately 12.75% of the confirmed positive cases, suggesting an increase in co-infection with dengue and CHIKV during the analysis period.

In contrast to CHIKV, dengue cases were not concentrated in just one region of the state. The South region exhibited the highest regional positivity rate in 2022 (40.8%) and 2023 (22.7%).

In conclusion, these researchers wrote, 'The study findings offer valuable insights into two arboviruses in Brazil, particularly in Minas Gerais. These high rates of re-emergence and co-infection with both arboviruses provide useful data for implementing control measures of Aedes vectors and the urgent implementation of public health politics to reduce the numbers of CHIKV and DENV cases in the country.'

To prevent infections, the PAHO suggests that international travelers discuss vaccination options with a travel vaccine expert at least one month before visiting these areas of Brazil. Approved vaccines for chikungunya (IXCHIQ) and dengue (Qdenga) are available.