There were epidemics of influenza-like illness during the winters of 1915-6 and 1916-7 when mortality was low among infants and children but high among older adults (like SARS-CoV-2 but not influenza). Records suggest that 'influenza' epidemics preceding the 1918-9 pandemic were caused by multiple respiratory viruses possibly an undocumented coronavirus.
Did coronaviruses cause 'influenza epidemics' prior to 1918?