A more contagious variant of Omicron is sweeping across America, but it doesn’t come close to the original’s severity

Since March, the BA.2 subvariant of Omicron, known as stealth Omicron, has been the dominant COVID-19 strain in the U.S., according to the Centers for Disease Control and Prevention (CDC). It now makes up 86% of total cases.

The subvariant, identified in January, is following the same path as its predecessors, initially finding a foothold on the coasts before spreading inland.

The subvariant can be up to 60% more transmissible than the original Omicron, able to infect people who have already received two doses of the vaccine and been boosted. However, those people may come down with only a mild case or show no symptoms at all.

Its “extraordinary” contagiousness, combined with most state and local mask and proof of vaccination mandates dropping across the U.S., is a “formula for spread,” says Dr. William Schaffner, a professor of infectious diseases at Vanderbilt University Medical Center.

As the subvariant began to gain steam last month, Dr. Anthony Fauci predicted it wouldn’t develop into as serious a surge as the original Omicron, citing widespread immunity in the general population from previous infections. Omicron peaked in February with a death rate approaching 3,000 people daily. With its BA.2’s growth rate already falling, Fauci’s prediction appears to be accurate. “We’re in a position right now to withstand what will likely be a bump rather than a big surge,” Eric Topol, a professor of molecular medicine at Scripps Research in San Diego, tells Fortune.

Schaffner says the surge isn’t impacting health care systems, the economy, or regular life as much as during previous large surges. “It simply is not nearly as severe, so it’s less of a public health problem,” he says. 

However, stealth Omicron’s relatively limited surge does not necessarily mean a gradual end to the pandemic, with variants becoming less severe over time as the virus embeds itself into the general population. It’s possible that a more virulent strain will emerge as the virus mutates.

“The perception shouldn’t  be that the coast is clear,” says Topol. “I wish it was, but we still have an ominous [threat] out there.” He notes that though BA.2 symptoms are milder for those who have been vaccinated or boosted or else have recently acquired immunity through infection, it’s still a serious threat for unprotected individuals.

Dr. Stuart Ray, a professor of medicine in the division of infectious diseases at Johns Hopkins University, points to recent recombinant strains of COVID as evidence of the virus’s continued unpredictability. Strains like “Deltacron” and Omicron XE show how “the virus is able to continue evolving when a high proportion of people are infected,” he says. “If we allow that to continue, we don’t know what the next virus will be.”

Ray says it’s impossible to predict what symptoms future variants might exhibit. COVID, no matter the strain, is generally an infection with two symptomatic phases, he says: a superficial upper respiratory infection often followed by an “immune-driven cycle of inflammation.” Omicron, he says, seems to have a relatively mild inflammatory phase. “There’s nothing about this process that makes us think that the next variant might not have a characteristic more like Delta, with a more severe inflammatory phase,” he says.

Ray acknowledges that public perception that the pandemic has entered a milder phase is correct when considering the relatively low hospitalization rate. However, “I think the danger is complacency about that,” he says, especially when immunocompromised individuals remain at risk.

That complacency “is understandable in simple human terms,” says Schaffner. “People have COVID fatigue, and there is a great eagerness to leave all the constraints and move into a new normal, which most people hope resembles the old normal very, very closely.” 

The urge to return to the old normal and the continued unpredictability of the virus lead to certain persistent questions, he says: “Will there be a new variant that crops up somewhere around the world that can evade the protection of our vaccines? Will we accept periodic boosting?” To date less than half of eligible Americans have been boosted, according to the CDC.

“I think we will have a lot of work ahead of us if we need periodic boosters of updated vaccines in the future,” says Schaffner—“trying to persuade people to get it, making them feel comfortable, and making them understand that that’s a responsible thing for them to do for themselves and for their families.”

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