Early data on Omicron show surging cases but milder symptoms
Two weeks after the Omicron variant was identified, hospitals are bracing for a covid-19 tsunami. In South Africa, where it has displaced Delta, cases are rising faster than in earlier waves. Each person with Omicron may infect 3-3.5 others. Delta’s most recent rate in the country was 0.8.
South Africa is not in lockdown, which may partly explain Omicron’s rapid spread. However, prior variants benefited from encountering lots of people with no immunity. By now, most South Africans have either recovered from covid or been vaccinated.
In such an environment, there are two ways Omicron could spread so fast. One is greater infectiousness, which depends on such factors as how easily it enters cells. The other is better evasion of immunity.