JN.1—a new, highly mutated COVID variant—could cause one of the largest U.S. waves yet, experts say. When each state could see the variant peak

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Respiratory pathogens are on the rise this winter in the U.S., with signs so far pointing toward a significant, but not outlandish, season—perhaps a bit of a respite after last winter’s “tripledemic.” 

The wildcard in the forecast, however, could change the scene entirely. “Pirola” JN.1, the highly mutated Omicron strain, could send COVID infections skyrocketing to the second loftiest level the U.S. has seen so far. Coupled with other winter illnesses like RSV and flu, hospital capacity could again be tested this season, experts tell Fortune. It depends on a number of factors, including how intensely the new variant spreads in the U.S., vaccination rates, and how well waning COVID population immunity holds up.

Already, JN.1 dominates U.S. COVID infections, according to estimates by the U.S. Centers for Disease Control and Prevention released Friday. In two weeks it surpassed the previously dominant variant, HV.1, and is now double its size, comprising 44% of the country’s COVID infections—leaving all past leading variants sitting in the single digits, far behind, in the dust.

Will HV.1 pick up Spike L455F/S to stay in the game or slowly make way to JN.1 family? https://t.co/kNNxIGLKtO

— Raj Rajnarayanan (@RajlabN) December 22, 2023

Some countries already seeing record highs

Hospitals currently aren’t under the same strain they have been during pandemic winters. Flu and RSV peaked early last year, putting undue pressure on the system early on. 

Whether this will remain the case will largely depend on the activity of “Pirola” JN.1, which could stress hospitals in some areas of the country if its wave lines up with flu and RSV waves, according to leading COVID forecaster Jay Weiland, oft cited by public health experts like Scripps Institute founder and director Dr. Eric Topol.

Already, some European countries like Germany, the Netherlands, and Denmark are seeing all-time high levels of COVID in wastewater, higher even than the Omicron spikes of early 2022, according to Weiland’s estimates.

COVID hospitalizations are rising in some countries like Singapore, which doesn’t see a true winter and, thus, doesn’t experience the typical seasonal spikes in respiratory diseases driven by increased indoor activity, weather, and similar factors.

Singapore hospitalizations rose again this week from their JN.1 Pirola surge.

Case incidence appears to have plateaued, so I think this is probably near the peak. pic.twitter.com/f4UpJp0gYV

— JWeiland (@JPWeiland) December 21, 2023

Hospitalizations may have peaked in Ile-de-France, the country’s most populous area. But their peak, if reached already, was higher than last winter’s, according to Weiland.

Encouraging signs that Ile-de-France *might* be peaking already from their Pirola wave. Peak height was higher than last winter, but sharper (if this is the peak) pic.twitter.com/MjkXhWpRuL

— JWeiland (@JPWeiland) December 21, 2023

COVID hospitalizations are on the rise in New York City, considered a bellwether for the rest of the U.S., Raj Rajnarayanan—assistant dean of research and associate professor at the New York Institute of Technology campus in Jonesboro, Ark., and a top COVID variant tracker—told Fortune. There, JN.1 is responsible more more than a third of sequenced COVID cases—and rising.

— Raj Rajnarayanan (@RajlabN) December 21, 2023

As of Monday, Weiland projected that there were nearly 1 million active COVID infections in the U.S. each day, with 1 in every 340 Americans becoming infected daily, and 1 in every 34 currently infected. Most COVID forecasters hung up their hats at the end of the national and global public health emergencies earlier this year, leaving no other long-term COVID forecasts to compare it to. The CDC’s, for instance, is updated every two weeks and only projects one day out.

Still, signals like wastewater are quickly trending upward, set to potentially eclipse the country’s second biggest wave, in late 2022, though not expected to rival the initial Omicron tsunami in January of that year. The CDC shows COVID wastewater levels appearing to crest as of Dec. 9, the most recent date for which data is available, in all areas of the U.S. except one—the Northeast, the first to be hit with a swell of JN.1.

December 18th Update:

Case increases continue, with JN.1 Pirola dominance expected within a week. Near 1 million/day, and not near the peak yet.

🔸965,000 new infections/day

🔸1 in every 340 became infected today

🔸1 in every 34 people currently infected pic.twitter.com/kE1NjTuFTU

— JWeiland (@JPWeiland) December 18, 2023

JN.1 is already dominant in New York and New Jersey, according to Weiland’s modeling, jiving with current regional trends in hospitalizations. He sees JN.1 peaking in Iowa, Illinois, Florida, Washington, and Oregon ahead of Christmas. 

About half of the remaining states—many in the southern half of the country—should see JN.1 peak sometime before New Year’s, he predicts. The other half—comprised of many northern states—is likely to see its crest sometime in January.

Timing for Pirola (JN.1) dominance in the US is going to vary a lot depending on location. Some states lack data and have been grouped in with surrounding states.

Earlier dominance will probably lead to faster increases over the holidays.

No data for Hawaii, Alaska. pic.twitter.com/0EPMvpu4PZ

— JWeiland (@JPWeiland) December 21, 2023

Low vaccine rates, no ‘herd immunity’

JN.1 aside, there’s good news: The level of U.S. COVID, flu, and RSV hospitalizations combined is currently sitting well below last year’s level at this time, down by about a third, according to the latest data from the U.S. Centers for Disease Control and Prevention. And updated COVID vaccines, released this fall, are expected to hold up against JN.1 when it comes to protecting against severe disease and death.

The not-so-great news: The winter respiratory season is still no joke—far from mild when compared to recent pre-pandemic seasons. Doctor visits for respiratory illnesses are above baseline across the country and have been for six consecutive weeks, according to the latest CDC influenza surveillance report. RSV hospitalization rates remain elevated and increasing among young children and older adults.

Vaccines—including a new RSV vaccine for older adults and a monoclonal antibody injection for infants, as well as an updated COVID-19 jab—are no doubt keeping hospitalizations at bay, Tom Cotter, executive director of nonprofit Healthcare Ready, told Fortune. The organization helps connect government, nonprofits, and medical supply chains to prepare for disasters.

But vaccine uptake is far from optimal. Less than 8% of U.S. children have received a COVID vaccine this year, while around 43% have received a flu vaccine. Among adults, only 18% have received an updated COVID vaccine, while around 42% have received the flu vaccine. Among adults 60 and older who are eligible to receive the new RSV vaccine, only 17% have, according to the latest data released by the CDC.

Bottom line: In the face of a winter “syndemic,” the U.S. isn’t helping itself nearly as much as it could be.

When it comes to COVID, especially, vaccination rates are “way too low to have any kind of community herd immunity,” Cotter said. But herd immunity is no longer the goal, he contends. The new aim: to preserve hospital capacity for those who need it most—those who will still need a hospital bed despite receiving the vaccine, especially the immunocompromised and elderly. 

Special efforts must be made to ensure historically marginalized populations have equal access to vaccinations and treatments, he added.

U.S. hospital systems learned some tough lessons last winter, Cotter said, when patient demand forced some to get creative, turning gift shops and play rooms into patient care areas, and resurrecting and repurposing abandoned NICUs with oxygen hook-ups.

While there is still work to be done, “pediatric hospitals and networks have done a good job of compiling the lessons learned from last year’s respiratory surge,” according to Cotter.

Such facilities have been preparing for another winter surge for an entire year, he added, updating triage plans for emergency departments and creating stockpiles of pediatric medical equipment to ward off shortages.

This winter season, there is much to be thankful for, Cotter contends—the aforementioned advances in emergency planning, and the march of technology onward, resulting in new, and better, vaccines against foes both familiar and new. But there won’t be much to celebrate if Americans don’t avail themselves to advances in science—particularly, if they don’t get vaccinated.

And while we needn’t worry about a repeat of winter 2021-2022, “the number of people around the country with COVID at the moment is still quite high,” Weiland cautioned.

In short: Keep waiting to exhale.

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