Flu cases are rebounding in Pennsylvania, with the upturn possibly fueled by the arrival of new flu strains.

Flu cases normally peak in January or February in Pennsylvania and then plummet. That seemed to be happening until about a month ago, when cases made an unusual U-turn.

The latest count of about 10,000 new cases during the week ending last Saturday is still well below the early January peak of about 14,600 new cases in one week.

As of Thursday, there didn’t appear to be an uptick in McKean County. On a state map showing rates for each county, McKean was at the lowest 25%, Cameron and Elk counties in the second to lowest, while Potter County was in the second highest.

The health department reported that McKean County has had 237 influenza cases since October, and 90 RSV cases. In Elk County, there have been 261 influenza cases and 88 RSV cases. Potter County had 210 influenza cases and 70 RSV cases. In Cameron County, there have been 49 influenza and 16 RSV cases.

Since most people with the flu don’t get tested, the test results reported to the state reflect only a fraction of the total.

It’s unusual but not unheard of for cases to rebound. For example, during the 2021-22 flu season, a late season rebound matched the peak that came at the normal time more than two months earlier.

Sometimes another strain of flu appears, causing a bump in cases. That might be happening now: The previous peak involved mostly the A/H1N1 strain, which remains the most common. However, the health department said prevalence of the B and A/H3 strains have been increasing.

Meanwhile, RSV cases continued to fall last week, as did the number of people admitted to the hospital with COVID-19.

As of Saturday, 270 Pennsylvania deaths were attributed to the flu during the respiratory illness season that officially began in October, and 1,726 deaths were listed as COVID-19-related.

(Era editor Marcie Schellhammer contributed to this report.)