The simple math that makes Omicron scary

Therein lies the danger possible with Omicron. “That small proportion of severe disease, if it’s multiplied by millions of cases, that will be bad,” says Jeffrey Barrett, the director of the COVID-19 Genomics Initiative at the Wellcome Sanger Institute. “I’m pretty worried.”

This is the simple math we have to keep in mind: A tiny percent of a huge number is still a big number. A largely mild but uncontrolled Omicron wave could cause a lot of pain, hospitalizations, and death across a country.

The ultimate impact of Omicron will depend on how tiny that tiny percent is and how huge that huge number is. We can’t say for sure, but we have some hints. Given the early trends out of South Africa, the U.K., and Denmark, a large Omicron wave is very possible, though not guaranteed. If we wanted to reassure ourselves, we could note that the absolute numbers of Omicron cases detected so far are so small, they may be skewed by chance, and we could be overestimating the variant’s growth by specifically searching for it. But Omicron is consistently increasing in the three countries looking hardest for it and therefore likely increasing quietly everywhere else.