The rate at which the omicron variant has spread is astounding. Bolstered by what appears to be a much higher rate of reproduction in the respiratory system, and what also appears to be a shortened period of incubation, omicron is spreading at a rate that’s difficult to believe. Numbers published last week set the percentage of new cases in the United States that could be attributed to omicron at 19%. On Monday, the Centers for Disease Control and Prevention (CDC) set that number at 73%. In a cluster of Northwest states—Oregon, Washington, and Idaho—omicron accounted for 96% percent of new cases in the last week. The rate of expansion in the U.S. mirrors what happened a week earlier in the U.K., where omicron went from a tiny percentage to the dominant strain in a matter of days. Both of these trends follow that of South Africa, where omicron now accounts for 96% of new cases. Omicron spreads more readily than previous variants. It spreads more quickly than previous variants. It is far more likely to reinfect those who have been ill from previous variants. It is more evasive of vaccines than previous variants. There is still no evidence it is milder than previous variants. Read more