It’s hypothesized that the common use of antibacterial soap is helping create super strains of bacteria that are resistant to antibiotics.
Why does this matter for a viral infection? Because the high death rates in the 1918 flu epidemic may have been caused by secondary infections.
Although my other posts have pointed out that hyper immune response to 1918 virus may have caused increased mortality, it may have been the condition caused by this hyper response (i.e, fluid in the lungs) that led to bacterial infection.