Enlarge / A box and a tablet of Roche Pharmaceuticals' Tamiflu pills for influenza. (credit: Nikos Pekiaridis/NurPhoto via Getty Images) Since reports emerged earlier this year that dairy cows across the country had been infected with H5N1 bird flu, the prospect that the virus could evolve to spark another pandemic has stoked serious concern. But unlike COVID-19, the flu is an old, well-known foe.