New Covid variants stoke fears of summer surge in cases

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New variants of Covid-19 are spreading around the world and stoking fears of a surge in cases in the United States over the summer, in the latest sign of the infectious disease’s ability to mutate and potentially threaten herd immunity.

kp. 2, one of several variants called FLiRT (the word derives from the names of mutations in the variants’ genetic code) has become the dominant coronavirus strain in the US since it first emerged in March.

In the two weeks until May 11, KP. 2 accounted for 28.2 percent of cases, up from just 3.8 percent in the two weeks through the end of March, according to the latest data from the U.S. Centers for Disease Control and Prevention. The KP1.1 variant has also grown rapidly to account for 7.6 percent of infections.

The agency is closely monitoring FLiRT variants, including the KP strains and the previously dominant JN.1 strain, which are all offshoots of the dominant Omicron Covid strain, but does not believe there is evidence that it is driving an increase in disease cases. serious.

Four and a half years after the outbreak of the pandemic, the number of cases in the United States has fallen near historic lows in recent months. But while many infectious disease experts don’t expect an increase in hospital admissions, they warn that this new group of variants could lead to a wave of infections in the summer.

A key question is how effective the current vaccines will be against the new strains. Lawrence Young, a virologist at the University of Warwick, said booster shots would still provide valuable protection, at least against serious illness.

However, William Schaffner, an infectious disease specialist at Vanderbilt University in Nashville, Tennessee, argued that protection “is not as guaranteed against these subvariants because the mutations are a little further removed from the kind of antibody protection we get from an infection.” prior and vaccination.” ”.

“But that evidence comes from laboratory studies, we need to see what happens in the field,” Schaffner added.

The US Food and Drug Administration’s vaccine advisory committee will meet at the end of the month to discuss recommendations for next winter’s variant mix of Covid vaccines. He postponed the early May meeting so he could gather more data on the latest strains.

In Europe, the World Health Organization said FLiRT variants had been detected in 14 countries in Europe, as well as in Israel.

However, the European Center for Disease Prevention and Control said Covid activity “remains low” across the continent, “although a small number of individual countries show slight increases in detections from very low levels.”

It also noted “a limited number of detections” of JN. 1.7 and kp. 2, the two variants that had increased in proportion in the US.

UK Health Security Agency officials said on Friday that several of the FLiRT strains were circulating in the UK at low levels, although some appeared to be increasing as a proportion of sequenced cases.

Young said the latest data indicated that infections in the United Kingdom with FLiRT variants, which had “overtaken some of the other variants,” would likely be similar levels to those seen in the United States. The strains are also becoming more prevalent in other countries, including Canada, Australia, Thailand and India, she added.

Paul Hunter, professor of medicine at the University of East Anglia, pointed to the latest data from the UKHSA which suggests hospitalizations are currently at stable levels and, while there has been a slight overall increase in positive cases, he stressed that it is unlikely leading to an increase in infection.

However, he added that while there was little evidence to suggest that FLiRT variants were inherently more infectious than previous dominant strains, they probably had a slight immunological advantage, “and in a population with waning immunity, that is likely to contribute to the spread.” of the illness”. the virus”.

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