Conversely, serum CXCL17 levels in severely ill coronavirus disease 2019 (COVID-19) patients and individuals with pulmonary tuberculosis (PTB) were not elevated, indicating that CXCL17 serum levels are a specific diagnostic marker that differentiate pandemic influenza A(H1N1) from other infections in patients with respiratory illness. This evidence concerns the gene CXCL17 and infection.