Coronavirus cases are skyrocketing in the United States and in many parts of the world, with the fast-spreading Omicron variant combining with lax public health measures and holiday gatherings to drive daily infections to pandemic-level highs. Here in the U.S., more than 200,000 people are testing positive for coronavirus each day — nearly reaching last winter’s peak — with the U.S. on pace to surpass 1 million daily infections in January. U.S. airlines canceled thousands of flights over the Christmas holiday, citing increasing rates of illness among flight crews. Meanwhile, many school districts and colleges have announced a return to online classes. Public health officials warn of a surge in pediatric COVID-19 cases, with northeastern hospitals seeing a fourfold increase in the number of children hospitalized in the past two weeks.