After two difficult COVID-19 winters, the current season of respiratory sickness already rivals some of the worst cold and flu seasons on record — and it started about two months early.

RSV, or respiratory syncytial virus, has made so many young children ill this fall that weekly pediatric hospitalizations for RSV are the highest recorded. Influenza, which normally peaks in February, has driven up hospitalization rates to the highest level for this time of year in more than a decade, surpassing hospitalizations from COVID-19. And while COVID illness is lower than it was the last two Decembers, it, too, is climbing.

Public health officials have been warning for weeks that a “tripledemic” of COVID-19, flu and RSV would strain an already weary health care system. Hospitalizations from the three viruses have been rising together. Nationally, RSV appears to have peaked, and flu is peaking in a few parts of the country, but infections from the two viruses are expected to plateau at high levels.

Experts say it is difficult to estimate the severity of the rest of this season because the coronavirus pandemic disrupted somewhat predictable patterns for other respiratory diseases.

“There’s a whole lot of winter left,” said Richard Webby, a virus expert at the St. Jude Children’s Research Hospital in Memphis, Tennessee. “Certainly there’s lots of time for another COVID wave and even enough potentially for another version of flu.”

The country has already faced two record-breaking seasons under COVID-19, which disproportionately affected older Americans, but the return of RSV and flu this year means that some of the burden of illness has shifted to the country’s youngest — and their families.

Weekly hospitalizations for RSV among children are the highest they have been since the Centers for Disease Control and Prevention began its surveillance in the 2018-19 season. Roughly 1 in every 70 babies 6 months and younger have been hospitalized since the beginning of October, according to preliminary estimates.

With flu surging and COVID-19 circulating, respiratory illness has overwhelmed pediatric units across the country, shifting the strain to emergency rooms and children’s hospitals.

“You ask people who are involved with either emergency services or hospitalizations, and they’ll tell you this is the worst season that they can remember,” said Dr. Daniel Rauch, chief of pediatric hospital medicine at Tufts Medical Center in Boston.

“We are pretty scared for the winter,” he added. “I don’t know that our staff can keep it up.”

RSV cases and hospitalizations appear to be peaking but some experts predict they will level off and remain high for some time.