Lipopolysaccharide (LPS) is usually found in Gram-negative bacterial walls and recognised by TLR4 [182]; despite SARS-CoV-2 not containing LPS, and thus not being directly recognised by TLR4, stimulation of this TLR is associated with the development of ARDS in COVID-19 patients, demonstrating the impact of bacterial stimulation on patient symptoms. This evidence concerns the gene TLR4 and acute respiratory distress syndrome.