Changes wrought by the Covid-19 pandemic are most likely driving the unusually early surge (in flu and RSV)

See RSV and Flu Are Making More Kids Sick This Year: Covid-19 spread, prevention measures kept other viruses in check last year by Brianna Abbott of The WSJ. Excerpts:

"But Dr. Havers and other public-health experts said changes wrought by the Covid-19 pandemic are most likely driving the unusually early surge. Covid-19 mitigation measures including masking and distancing appeared to have had a marked effect on the circulation of other viruses, suppressing their spread and throwing them off their seasonal pattern. That likely left lower levels of immunity in the population.

“It reflects the pool of children who hadn’t experienced their first RSV season,” said Maria Asuncion Mejias, a principal investigator in the Center for Vaccines and Immunity at the Research Institute at Nationwide Children’s Hospital. “They’re kind of catching up.”"