Despite of the introduction of SARS-CoV-2 on Giglio Island by five cases, known to have had physical interaction with local population, our study found one asymptomatic subject, positive to IgM but negative to RT-qPCR and confirmed the absence of either current or past viral infection in 633 residents of this highly populated area through qualitative assessment of anti-SARS-CoV-2 antibodies and RNA in saliva. This evidence concerns the gene CD40LG and viral infectious disease.