Virol J. 2026 Feb 3. doi: 10.1186/s12985-026-03088-3. Online ahead of print.
ABSTRACT
BACKGROUND: West Nile virus (WNV) is primarily transmitted by the bite of Culex mosquitoes, but other mechanisms, such as blood transfusion, have also been described. Since its identification in the Americas in 1999, WNV has circulated consistently in the United States of America (USA); however, although WNV has been detected in humans in South America, no major outbreaks have occurred in more than 20 years. One of the hypotheses to explain this difference is the underdiagnosis of the infection. In Mexico, nine isolated cases have been officially reported since 2003 despite its proximity to the USA. In this study, we aim to demonstrate the circulation of WNV in blood donors from a northern border city of Mexico.
METHODS: Between August and September of 2023, 86 serum samples from volunteer blood donors were collected to determine anti-WNV Immunoglobulin (Ig) G using a commercial enzyme-linked immunosorbent assay (ELISA) kit. In a subgroup of 44 samples, anti-WNV IgM was determined. To corroborate the IgM results, nucleic acid amplification tests (NAAT) were performed to determine RNA of WNV, Dengue and Zika. The participants were questioned about the history of travel to the USA; all of them were residents of the city of Nogales, Sonora, located on the border with the state of Arizona. For the comparison of seronegative and seropositive donor groups, the Chi-square test and Mann-Whitney U test were used for qualitative and quantitative variables, respectively. Additionally, a spatial analysis of seropositive cases was conducted.
RESULTS: One sample was reactive to anti-WNV IgM and IgG; however, all NAAT results were negative. In addition, 19 samples were reactive for IgG, and no statistically significant differences were found between the groups. Seropositive cases showed a geographic pattern of clustering on the outskirts of the city, in areas with low population density.
CONCLUSIONS: Our results strongly suggest recent WNV circulation among residents from the northern border of Mexico. The lack of differences regarding the history and frequency of travel to the USA suggests that contact with the virus occurs in Mexico and that the low reported circulation in the region represents an underdiagnosis of the disease.
PMID:41634716 | DOI:10.1186/s12985-026-03088-3
