For thousands of people in the Philadelphia region, the end of 2014 was accompanied by fever, cough, and body aches.
Reported flu cases in Pennsylvania climbed sharply over the final weeks of December.
Tests had confirmed more than 10,000 influenza cases this fall and winter as of Saturday, according to the state Department of Health. The actual number of sick people is likely many times higher, as the vast majority do not get laboratory tests.
Flu activity was also rising in New Jersey, but less severely locally. State health officials report generally high overall flu levels - but say reports are low in South Jersey. Actual numbers are reported differently than in Pennsylvania and are not comparable.
About 4,500 of the Pennsylvania cases were reported last week alone, and the Health Department in Harrisburg says flu activity is widespread in the state.
The increase has arrived earlier in flu season than in most recent years. More commonly, reported cases in Pennsylvania start to climb in late January or February.
The predominant strain this season tends to cause more serious illness, and the vaccine being administered this year is not well matched to it. Still, health officials urge everyone 6 months and older to be vaccinated, saying it offers some protection.
Since early December, confirmed flu cases have jumped in the region. The state reported 178 in Philadelphia, 369 in Bucks County, 323 in Chester County, 279 in Delaware County, and 591 in Montgomery County. Just a few dozen cases had been reported in each county as of Dec. 6.
So far, Allegheny County has reported the most cases in the state: 1,332.
Influenza-associated deaths have also risen in recent weeks, with 16 linked to the virus now reported in Pennsylvania. Thirteen of the victims were 65 or older.
An estimated 120 to 2,000 people die of flu complications each year in the state. Many states, including New Jersey, do not report total flu deaths, and the U.S. Centers for Disease Control and Prevention does not collect them. Researchers using complex models estimate that tens of thousands of people, most of them elderly, die each year nationwide from flu-related complications such as pneumonia.
Reports of flu cases are picking up across the country, with patterns varying from state to state. Pennsylvania, New Jersey, and 34 other states are among those listed with widespread flu activity, according to the CDC's most recent flu report, through Dec. 20.
Flu season generally runs from October to May, typically peaking between December and February, the CDC says.