Rising Concerns Over Mild U.S. Bird Flu Cases and Pandemic Risks

Despite a significant increase in human H5N1 bird flu cases in the U.S., all have been mild, puzzling scientists given the virus's historically high fatality rate. Researchers are exploring various hypotheses, including the mode of transmission, the specific virus strain, and potential pre-existing immunity from exposure to similar viruses. The mildness of U.S. cases contrasts with more severe cases in Asia, raising questions about the virus's true pathogenicity and the accuracy of previous fatality estimates.