CNN —
Levels of coronavirus disease (Covid-19) in the United States are near the lowest on record, but new virus variants threaten to emerge again as the country heads into summer, disrupting the downward trend. .
KP.2, one of the so-called FLiRT variants, has overtaken JN.1 to become the most prevalent coronavirus variant in the United States, according to data from the Centers for Disease Control and Prevention. Data up to May 11 shows the virus accounts for more than a quarter of the country's infections, almost twice as many as JN.1. A related variant, KP.1.1, causes about 7% of cases, according to CDC data.
The FLiRT variants are descendants of the JN.1 variant that caused this winter's wave, and are all part of the broader Omicron family. The acronym in the name refers to the position of the amino acid mutation found in the virus. Some locations help the virus evade the body's immune response, while other locations help the virus become more infectious.
Variants of the new coronavirus are “accumulative mutations that do one of two things: antibodies built up through vaccination or infection are no longer able to bind to the virus (this is called escaping immunity); or That's how viruses bind to cells,” said Dr. Andy Pekosch, a virologist at the Johns Hopkins Bloomberg School of Public Health.
This has become a familiar pattern for how the virus that causes Covid-19 continues to evolve, but experts are unsure where the changes will occur next or if they will cause the virus to continue evolving. He said there is not enough knowledge yet to predict exactly how the virus will affect infection routes. population.
Mutations in the FLiRT variant pose a major threat to increased transmissibility and the possibility of a summer wave. Covid-19 has settled into some seasonal patterns over the past few years, including a summer surge, but the exact level of risk this year is unclear.
“In the past, we've had some variants that are initially strong but then don't take over. These subvariants can become predominant over time or account for between 20% and 40% of cases. It's possible that it's going to get worse and stay there. We'll just have to wait and see,” said Dr. William Schaffner, an infectious disease expert at Vanderbilt University. “The virus still has an impact. It tells us what it's going to do. All of our crystal balls are pretty cloudy.”
Surveillance of coronavirus infections has been significantly reduced since the U.S. public health emergency ended a year ago, also increasing uncertainty. However, the available data are consistent. At this time, wastewater monitoring shows that virus activity is very low and declining in all regions of the country, and hospitalization rates due to COVID-19 remain extremely low.
“From what we've heard from the lab, so far the FLiRT variant appears to be just as contagious as other Omicron variants, indicating that this is actually highly contagious. “But they don't seem to cause more severe disease or any disease that is distinctive in terms of clinical symptoms,” Schaffner said.
As of May 1, the requirement for all hospitals to report COVID-19 data to the federal government has expired. But Schaffner's Vanderbilt University Medical Center is part of a CDC-run surveillance network that continues to track trends based on a sample of hospitals that cover about 10% of the U.S. population. The hospitalization rate for COVID-19 has fallen from nearly 8 new hospitalizations per 100,000 people in the first week of this year to about 1 new hospitalization per 100,000 people by the end of April, data shows. did.
While the FLiRT variant poses some risk this summer, experts remain focused on what happens in the fall.
“If I were to predict, I think we'll see a few more cases this summer, potentially a slight spike. But in the fall, it's really going to be about which variants are present. “It will be,” Pekos said. “The fall is probably when we would expect a surge in coronavirus cases. And if there are variants out there that have a lot of these mutations that evade immunity, we'll see an even bigger surge in the fall. It's more likely.”
He said fall and winter pose a greater risk because people's immunity is higher.
“Currently, viruses need better conditions to transmit, and those better transmission conditions are likely due to cooler weather and people spending more time indoors, creating an environment in which respiratory virus transmission can occur. It will likely happen in the fall when it is more likely to be 'more efficient. ”
The study, published Wednesday in the medical journal JAMA, is a reminder of the burden COVID-19 continues to place on the United States. While hospitalization rates for coronavirus infections were much lower this winter than in previous years, they were still more deadly than the flu. In a study of thousands of hospitalized patients, the mortality rate for patients with COVID-19 was 5.7%, compared to 4.2% for patients hospitalized with influenza. In other words, COVID-19 had about a 35% higher risk of death than influenza.
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People who received the latest COVID-19 vaccines this fall may still have some protection against the latest variants. Although the vaccine targets a different strain, it has been found to be equally effective against JN.1, and experts say some of these benefits may extend to FLiRT's relatives. It says that there is a sex. People who have been infected recently, especially since the beginning of this year when JN.1 was prominent, may also have some protection. However, immunity declines over time.
The U.S. Food and Drug Administration's Vaccine Advisory Committee is scheduled to meet in June to discuss recommendations for coronavirus vaccines to be released this fall. According to a post on the federal agency's website, the meeting will be held for about 30 days “to have more up-to-date information when making discussions and recommendations” and “to allow additional time to obtain surveillance data.” It has been postponed for a week.
For now, experts say the risk remains relatively low.
“As with all things COVID-19, our outlook could change in a week or two, but at the moment we are in a really, really good place and we are in the best position we have been in a long time. I was in position,” Schaffner said.
