Dhruv Khullar writes:

The Covid-19 pandemic, like every pandemic before it, is a story of equilibriums: between viral biology and human immune response; between news of the pathogen and fear of it; between the damage it inflicts and the social, economic, and political choices we make. A disease persists as a pandemic as long as these forces remain in flux; it becomes endemic when the balance is, more or less, set. The morning after Thanksgiving, Americans awoke to an unsettling revelation: Omicron, a highly mutated version of the coronavirus, with an unprecedented number of genetic changes, had been detected in southern Africa. Since then, it has appeared in dozens of countries across six continents and in at least twenty-two states. Our equilibrium has shifted again. But what, exactly, has changed?

An early sketch of the Omicron variant is coming into focus. It is, almost certainly, more transmissible than the Delta variant, which itself spreads more than twice as fast as the original strain. In mid-November, South Africa recorded an average of three hundred coronavirus cases a day; only about two per cent of tests returned positive. The country now routinely logs fifteen thousand cases a day, and the test-positivity rate has soared more than tenfold. But Omicron hasn’t overwhelmed the South African health-care system, even in Gauteng Province, where it first started to spread.

Earlier this month, doctors at the Steve Biko/Tshwane District Hospital Complex, a major medical center in Pretoria, released a report describing the clinical condition of Covid patients admitted during the current surge. On December 2nd, there were forty-two patients, of whom just fourteen required supportive oxygen (and not all necessarily because of the virus), and only one was admitted to the I.C.U. In recent weeks, the average length of hospitalization was three days, compared with about nine in the past; the mortality rate has been roughly a third of what it was. “I’ve never seen this picture before,” Fareed Abdullah, the report’s lead author, said. “At this stage of the beginning of the fourth wave, the main presentation is incidental Covid”—patients who came in for other reasons and happened to be carrying the virus.

Although these findings are encouraging, it’s important not to place too much stock in them. Most recent patients at the Tshwane District Hospital have been under the age of fifty—a group with a relatively low risk for severe illness, and, in South Africa, a very low immunization rate. It’s also possible that some of Omicron’s perceived “mildness” is a reflection of its immune-evasiveness: early evidence suggests that it may be nearly three times as likely as other variants to cause repeat infections. If Omicron leads to milder symptoms in people who haven’t previously been infected or vaccinated, that would be reason for comfort; if, instead, it produces illness requiring hospitalization in those who’ve survived a prior infection, that’s cause for concern. [Continue reading…]