This week, the Centers for Disease Control and Prevention announced that there is a new top dog among COVID-19 variants in the United States: a subvariant called omicron BA.2.
It is closely related to BA.1 omicron, which has caused the recent surge in infections, but BA.2 may be slightly more transmissible.
Both subvariants were present last November when the World Health Organization first identified Omicron as a variant of concern. It is unclear why BA.1 first spread globally and why BA.2 is now catching up.
Marcel Curlin, associate professor of medicine at Oregon Health & Science University, said the BA.1 subvariant may have gained an accidental, early advantage. For example, it may have been the first to reach a global transportation hub like London, allowing it to spread efficiently.
Now, with its obvious advantage in human-to-human transmission, BA.2 has the edge.
Subvariant BA.2 is now responsible for more than half of COVID-19 cases in the United States, and state-level surveillance shows it accounts for a growing percentage of cases in Oregon.
But all of this is happening against the backdrop of a global decline in cases.
Experts say that while BA.2 will outperform the other Omicron variants, it’s unlikely to see a large increase in cases in the process.
“Most people, myself included, don’t think that’s going to happen,” Curlin said. “It’s not going to trigger a big spike in new cases like the original Omicron wave.”
A key reason for this optimistic prognosis: Early research suggests that the BA.2 variant is relatively unlikely to reinfect people who had its close relative, BA.1.
Curlin said the BA.2 variant is causing problems in places like Hong Kong, where much of the population has not yet been exposed to COVID-19 and a lower percentage of people have received an effective vaccine and a booster shot.
In contrast, in the US, most people have either contracted the virus, gotten vaccinated, or both, which will likely put a damper on any potential new wave.
Still, Curlin said there are some early signs in sewage monitoring data that COVID-19 infection numbers are rising slightly.
Older adults and people with factors such as obesity and immunosuppression are at increased risk from the virus as community transmission increases and should prioritize their booster shots.
The CDC recently recommended an additional booster shot for people age 50 and older.
Curlin said the same public health messages about staying healthy during the pandemic remain true. The majority of people can experience milder symptoms, but infection can be serious and even fatal. You can reduce your risk by covering yourself in crowded indoor areas.
People should weigh their own health and that of those around them who are at risk – for example children who are too young to be vaccinated.
“We are in an era of personal judgment and responsibility,” he said.
Oregon’s COVID-19 hospitalizations are just 10% of the peak they hit in February, and case counts are near the lowest they’ve been since the pandemic began.