California’s summer COVID surge has proved to be particularly strong and enduring, as it storms to levels not seen in summertime in over two years.

California’s summer COVID surge has proved to be particularly strong and enduring, surprising experts with its tenacity as it storms into a third month.

The strength of this summer’s COVID surge probably is largely related to the ever-more infectious subvariants that continue to emerge as the coronavirus evolves, said Dr. Elizabeth Hudson, regional chief of infectious disease at Kaiser Permanente Southern California. A dizzying number of related subvariants — collectively dubbed FLiRT — have emerged in recent months. One in particular, KP.3.1.1, has been picking up steam at a startling pace and has become the most common strain nationwide.