What omicron's fast spread could mean for the U.S.

"Even if omicron does end up being less severe than delta and not as many people get very ill, ... there's plenty of reason for concern given just how contagious it appears to be: 'A small proportion of a huge number all at once can still overwhelm health care systems.' This is especially true in a country like the U.S. where many hospitals are already filled with COVID-19 patients who are sick – not from omicron – but from delta."