COVID-19 cases continue to fall in the United States, but parts of Europe and Asia are seeing spikes in coronavirus cases due to BA.2 — a subvariant of Omicron. It remains un-clear if BA.2 will cause a similar spike in the U.S., but experts believe cases will go up. Andrew Pekosz is a professor of Microbiology and Immunology at Johns Hopskins Bloomberg School of Public Health. Professor Pekosz explains what BA.2 is and how we should respond to it.