Outbreak of Chikungunya Fever in the Central Valley of Chiapas, Mexico

Abstract

Chikungunya virus (CHIKV) was isolated from humans in an outbreak of a febrile illness during July and August 2015 in the central valleys of Chiapas, Mexico. Sera obtained from 80 patients were tested for CHIKV RNA by reverse transcriptase polymerase chain reaction (RT-PCR) and for IgM and IgG antibodies by an enzyme linked immunoassay and a commercial indirect immunofluorescence test for CHIKV and dengue virus (DENV). Of the 80 patients, 67 were positive, including 50 for RNA and 17 for IgM. In addition, one patient was coinfected with CHIKV-DENV and 40 patients were positive for IgG antibody to DENV. The clinical manifestations included a high fever, polyarthralgia, headache, myalgia, rash, digestive disorders, conjunctivitis, and adenopathy associated with cervical and axillary inguinal regions. Complete nucleotide sequences of two of the CHIKV isolates showed that they belonged to the Asian lineage but did not group with other Mexican CHIKV isolates from the Chiapas coast. Our findings documented that different Asian lineage strains of CHIKV were circulating simultaneously during the 2015 outbreak in the Central Valley of Chiapas, Mexico. The 2024 cases suggest an explosive scenario of re-emergence of thousands of new Chikungunya and dengue fever (DENF) cases associated with deaths, and a dangerous increase of the four DENV serotypes throughout the Americas, especially in South American countries that have shown a high influx of human migration to southern Mexico. In Mexico, the state of Chiapas and other southern regions are the most vulnerable.

Keywords: Chiapas; Chikungunya; Dengue; IgM and IgG antibody; Mexico; viral RNA.

Fig 1.

Map of Chiapas, Mexico showing the sites where serum samples were obtained to test for Chikungunya virus in 2015.

Fig 2.

The results for testing sera sample obtained from suspected chikungunya fever cases by a commercial indirect immunofluorescent antibody assay during an outbreak of chikungunya fever in 2015 in Chiapas, Mexico.

Fig 3.

Phylogenetic analysis of CHIKV isolates obtained from patients during an outbreak of chikungunya fever in Chiapas, Mexico. Maximum-likelihood tree based on the full genome sequences (minus the 5’ and 3’ UTRs) of 143 geographically and temporally diverse strains of CHIKV from GenBank, along with strains 2107 and 2115 (highlighted with red and bold text). Branch lengths are scaled relative to substitutions. Bootstrapping was performed with 1,000 iterations; values ≥80 are represented as closed black circles at the node in the full phylogenetic tree (right), and are listed as text in the expanded view of the Asian lineage strains from the Americas and Caribbean (left).