Two new COVID-19 subvariants, collectively known as FLiRT, are gradually replacing the dominant winter strain ahead of a possible rise in coronavirus infections in the summer.
Infectious disease expert Dr. Peter Chin-Hong said the new FLiRT subvariants, formally known as KP.2 and KP.1.1, are believed to be about 20 times more contagious than their parent variant JN.1, the dominant subvariant during the winter. %.
Together, the two FLiRT subtypes accounted for an estimated 35% of coronavirus infections nationwide in the two weeks starting April 28, according to the Centers for Disease Control and Prevention. By comparison, JN.1 is currently thought to account for 16% of infections; in mid-winter, it was blamed for more than 80% of cases.
“We haven’t had a new dominant variant in the United States for a while,” said Dr. David Bronstein, an infectious disease expert at Kaiser Permanente in Southern California. “As each of these variants replaces the previous variant, we do see an increase in transmissibility – more easily spread from person to person. So, that’s what FLiRT is really concerned about.
The largest FLiRT subvariant, KP.2, is growing particularly rapidly in its proportion of existing coronavirus infections. At the end of March, the cases accounted for just 4% of estimated infections nationwide; more recently it was estimated at 28.2%.
Due to mutations in the evolved COVID-19 virus, the new subvariant is called FLiRT. “So instead of ‘L’, it’s ‘F’.” Instead of ‘T’, it’s ‘R’. Then they put an ‘i’ in it to make it cute,” Chin-Hong said.
Despite the increased transmissibility, the new mutations do not appear to cause more severe disease. Given that the new subvariant is only slightly different from the winter version, the vaccine is expected to continue to work well.
The addition of the sub-variant also comes as COVID-19 hospitalizations hit record lows. There were 5,098 hospital admissions in the week to April 27, just one-seventh of this winter’s peak, and 35,137 in the week to January 6.
However, as of May 1, hospitals across the country are no longer required to report COVID-19 admissions to the U.S. Department of Health and Human Services; now only voluntarily submitted data will be released nationwide.
In Los Angeles County, COVID-19 levels appear to be calm. For the week ending April 27, coronavirus levels in Los Angeles County wastewater were only 8% of their winter peak levels.
Still, some doctors say they wouldn’t be surprised if COVID-19 cases rise over the summer — as has happened in previous seasons.
“By the summer, we expect people’s immunity to be a little lower,” Chin-Hong said. For people who are older or immunocompromised, “they are at risk for more severe disease.”
Additionally, people often gather indoors to escape the heat during the summer, which increases the risk of transmission in crowded public spaces.
Chin-Hong said he sees severely ill COVID-19 patients at UCSF “who are either very old or severely immunocompromised and have not received a recent shot.”
Doctors say the FLiRT subvariant spreads more easily, underscoring how important it is for high-risk groups to stay vaccinated and stay away from people who are sick.
While the long-term likelihood of COVID-19 may be lower than in the early days of the pandemic, it is still here.
Data shows many people have not recently received a COVID-19 vaccine. In the week ending February 24, 29% of seniors nationwide had received one dose of the newer vaccine, which became available in September. As of April 30, about 36% of seniors in California had received updated doses.
“We’re still seeing hospitalizations and adverse outcomes and even people passing away from COVID-19. It’s not going away,” Bronstein said. “The good news is … the vaccine is still very effective at protecting you against hospitalization, serious consequences and death.”
According to the CDC, more than 42,000 COVID-19 deaths were recorded nationwide between October and April. This is significantly higher than the estimated number of influenza deaths during the same period: 24,000.
Still, the figure is lower than a comparable period last season, when more than 70,000 COVID-19 deaths were reported. This number is far smaller than the previous two devastating pandemic winters: between October 2021 and April 2022, more than 272,000 deaths were recorded; between October 2020 and April 2021, the number was more than 370,000.
The Centers for Disease Control and Prevention (CDC) recommended in February that people 65 and older get a second dose of an updated vaccine if at least four months have passed since their last shot. The CDC also says everyone 6 months and older should get a dose of the updated vaccine.
“Right now, the most important thing people can do is get vaccinated,” Brownstein said. He recommended that those who are particularly vulnerable continue to wear masks if possible, especially in places such as crowded airports and planes.
Additionally, he said it’s important for people who are sick to stay home to avoid spreading germs to others, especially older adults. If someone who is sick must leave their home, they should wear a mask around other people.
“Even in the summer, something that feels like a cold could actually be a COVID-19 infection,” Brownstein said. “We need to make sure that if you’re sick, we’re testing as much as possible, staying home… and making sure that you symptoms are milder before deciding to resume normal activities.”
California recommends that people with COVID-19 symptoms stay home until their symptoms are mild and improving and they are fever-free for 24 hours without medication.
They should also wear a mask around others indoors for 10 days after becoming ill, or if asymptomatic, after testing positive. They can stop wearing masks more quickly if they have two negative rapid tests in a row at least a day apart. But they should avoid contact with all high-risk groups for 10 days, according to the state Department of Public Health.
Before planning travel this summer, Chin-Hong recommends seniors talk to their health care provider to make sure Paxlovid can be prescribed without interfering with other medications if they become infected with COVID-19. Paxlovid is an antiviral drug that can reduce the risk of hospitalization and death when taken by people at risk for severe COVID-19 who have mild to moderate illness.
Chin-Hong also suggested that it makes sense for health care providers to prescribe Paxlovid as a “just in case” for high-risk people who plan to travel where the drug may not be readily available. Because Paxlovid has received full approval from the U.S. Food and Drug Administration, clinicians have this discretion, which gives healthcare providers more leeway in deciding when to prescribe the drug.
Earlier this year, another drug was made available to help protect the most vulnerable, such as cancer patients and organ transplant recipients. This is a monoclonal antibody called Pemgarda, which is injected intravenously every three months. It is authorized by the FDA for emergency use and can be administered prophylactically to help prevent recipients from contracting COVID-19 if they are exposed to an infected person in the future.
It is also expected that a new version of the COVID-19 vaccine may be released in September. Chin-Hong said it may have been designed to target last winter’s JN.1 strain, but officials may also believe it should be designed to target the emerging FLiRT subvariant.
