Environmental surface contamination in pilgrim transport vehicles during the Grand Magal of Touba: Molecular evidence from a preliminary study

Mass gatherings such as the Grand Magal of Touba (GMT) involve intense population mobility and prolonged close contact, creating conditions favorable to infectious disease transmission. While human-to-human transmission has been extensively studied, the contribution of environmental surface contamination in transport vehicles used by pilgrims remains poorly documented. During the August 2024 Grand Magal of Touba, environmental surface sampling was conducted in two minibuses transporting pilgrims from the Senegalese villages of Dielmo and Ndiop to Touba and back. A total of 102 samples were collected from frequently touched surfaces at three time points: before departure, upon arrival in Touba, and after return to the villages. Viral, bacterial, and gastrointestinal pathogen DNA/RNA were detected using quantitative real-time PCR (qPCR) targeting respiratory viruses and bacteria as well as enteric pathogens. Detection was defined by amplification below the assay cycle-threshold positivity cutoff, indicating the presence of pathogen nucleic acids. Respiratory bacterial DNA was frequently detected, particularly Staphylococcus aureus (41.7–53.8% of samples across time points) and Klebsiella pneumoniae (46.1–62.1% before departure and 50.0–63.1% after return), with markedly lower detection upon arrival in Touba (8.1–17.6%). Among respiratory viruses, only SARS-CoV-2 RNA was detected before departure (7.7–13.8%) and after return (5.3–16.7%) but not upon arrival. Gastrointestinal pathogens were largely absent, with only sporadic detection of enteropathogenic Escherichia coli . This preliminary study provides molecular evidence of environmental surface contamination in pilgrim transport vehicles during the GMT. Detection of pathogen nucleic acids suggests that transport environments may reflect microbial circulation among pilgrims, although qPCR results do not indicate pathogen viability or transmission risk. Environmental sampling in transport settings may complement surveillance strategies for mass gatherings involving highly mobile populations.