Symptomatically. Cases of influenza a where the person thinks they only have a minor head cold do exist and are a good fraction of all cases. Almost everyone ge

Symptomatically. Cases of influenza a where the person thinks they only have a minor head cold do exist and are a good fraction of all cases. Almost everyone gets influenza a every few years. It's just that many cases are asymptomatic or minor. Reconstructing household transmission dynamics to estimate the infectiousness of asymptomatic influenza virus infections https://www.pnas.org/doi/10.1073/pnas.2304750120 https://www.pnas.org/doi/10.1073/pnas.2304750120 "Symptomatic cases account for 68% (95% CrI: 63%, 72%) of infected children and 59% (95% CrI: 53%, 64%) of infected adults." Nearly half of adult influenza a infections are asymptomatic and go unreported and untested.