Exposure to non-endemic arboviruses (alphaviruses) in Costa Rica assessed from human samples collected in areas with contrasting levels of dengue endemicity

Abstract

Arboviruses represent a global public health challenge. The lack of diagnosticprotocols and the presence of asymptomatic infections complicate confirmatorydiagnostics. Alphaviruses, such as the equine encephalitis viruses, can cause severeoutbreaks and are usually misdiagnosed as dengue. Thus, evidence for theircirculation was assessed here. Plaque reduction neutralization test (PRNT) wasused to compare sera collected during 2022–2023 from an area with high dengueendemicity (Hone Creek) with another with low endemicity (Great MetropolitanArea, GMA) to elucidate the putative alphavirus circulation and determine whetherthere were differences between the two areas. The screening results of PRNT50%against the Venezuelan equine encephalitis virus (VEEV) and the Eastern equineencephalitis virus showed that 20.5% of sera collected from Hone Creek werepositive for VEEV, with 15.4% (n = 40) showing real neutralizing titers. In the GMA,only 0.8% tested positive for VEEV during the screening, with only 0.3% (n = 1)showing a true neutralizing titer. No sample was positive for the Eastern equineencephalitis virus or Mayaro (MAYV) and one serum sample from Hone Creek waschikungunya positive. This study underscores the global health challenge posedby arboviruses with their similar clinical presentation and antibody cross-reactivity,particularly in tropical regions where flaviviruses and alphaviruses prevail and cocirculate.The comparison of PRNT results between high and low dengue-endemicareas in Costa Rica shed light on the potential circulation of the VEEV and thefact that there is no circulation of Eastern equine encephalitis virus or Mayaroyet. These findings indicate a higher prevalence of VEEV in the high-endemicarea, emphasizing the importance of targeted surveillance, control measures,and better diagnostics.