As the global COVID-19 pandemic continues into its third year, the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, is focusing on preparing for a range of other viral threats that could cause a public health emergency. For decades, NIAID has launched major research responses and developed medical countermeasures to combat multiple emerging infectious diseases, including HIV/AIDS, SARS-CoV-1, Middle East respiratory syndrome coronavirus (MERS-CoV), Ebola virus, Zika virus, and SARS-CoV-2.