At her kitchen table, Kathy Spencer sorts the dozens of pills she must take since contracting COVID-19 in November 2020. Spencer was a teacher who liked to swim, work out and ride motorcycles long distance. Since getting sick in November 2020, she has s...

At her kitchen table, Kathy Spencer sorts the dozens of pills she must take since contracting COVID-19 in November 2020. Spencer was a teacher who liked to swim, work out and ride motorcycles long distance. Since getting sick in November 2020, she has serious lung problems, among other symptoms, and requires oxygen 24 hours a day. At one point she had 291 medical appointments over a 365-day period. (Mark Mirko/Hartford Courant/TNS)

LOS ANGELES — As highly infectious omicron subvariants continue to fuel a new coronavirus wave, there is growing concern about long COVID, in which symptoms or increased risk of illness can persist for months or even years.

Efforts to understand the scale of long COVID’s effects have taken on additional urgency given the number of people who have come down with the virus since omicron was first detected in California shortly after Thanksgiving. Some experts think this latest surge may exceed the record-high case counts seen over the fall and winter, leaving more people at risk of developing the condition.