The nation’s early flu season continued to grow in the U.S. this week, with no sign yet of a peak in the spread of coughing, achy, feverish illness, health officials said Friday.

“I think we’re still accelerating,” said Tom Skinner, a CDC spokesman.

Twenty-nine states and New York City reported high levels of flu activity, up from 16 states and NYC the previous week. Flu was widespread in 41 states, up from 31 states, according to the latest figures from the Centers for Disease Control and Prevention.

As of the week ending Dec. 29, 2,257 people had been hospitalized with flu, and 18 children had died from complications of the illness, CDC reported.

“It’s about five weeks ahead of the average flu season,” said Lyn Finelli, lead of the surveillance and response team that monitors influenza for the CDC’s National Center for Immunization and Respiratory Diseases. “We haven’t seen such an early season since 2003 to 2004.”

That’s the year that Joe Lastinger’s 3-year-old daughter, Emily, fell ill with the flu in late January and died five days later.

“That was the first really bad season for children in a while,” said Lastinger, 40, who lives near Dallas, Texas. “For whatever reason that’s not well understood, it affected her and it killed her.”

During that season, illnesses peaked in early to mid-December, followed by a peak in flu-related pneumonia and deaths in early January. It was over by mid-February and was considered a “moderately severe” season for flu, according to the CDC.  Finelli and other CDC officials say it’s too early to tell exactly how bad this year’s season will be.

But over at Google Flu Trends, which monitors flu activity in the U.S. and around the world based on internet search terms, this year’s season has already topped the bright-red “intense” category.

And at Flu Near You, a new real-time tracking tool that’s gaining about 100 participants each week, about 4 percent of the 10,000 users say they’ve come down with flu symptoms.

Joe Lastinger’s 3-year-old daughter, Emily, fell ill with the flu in late January 2004 and died five days later.

“That’s huge,” says John Brownstein, an epidemiologist and assistant professor of pediatrics at Harvard Medical School and Children’s Hospital Boston. “Last year, we never got near this.”

Brownstein is one of the founders of the project coordinated by Children’s Hospital Boston, the Skoll Global Threats Fund and the American Public Health Association. Though it’s still in its early stages, it already has generated new, interesting and, most of all, immediate data about this year’s flu season.

“It’s what we call ‘nowcasting,’” Brownstein said. “It’s a more up-to-date view.”

CDC data, which is based on visits to doctors for influenza-like illness, can lag two weeks or more behind real-time activity.

By contrast, Flu Near You can paint an immediate picture of what’s new with flu.

For instance, Brownstein said his data show that cough is the most frequently reported flu symptom this season, at 19 percent. It’s been followed by sore throat, 16 percent; fatigue, 15 percent; headache, 14 percent; body ache, 10 percent and fever, just 7 percent.

More telling, for people who reported both flu symptoms and vaccination status, of those who got the flu, three out of four were not vaccinated, while a quarter had gotten their flu shots.

Brownstein cautioned that can’t be used as a true measure of this season’s vaccine efficacy because of variables in reporting. But the CDC says that in the 2010-2011 flu season, vaccine effectiveness was about 60 percent for all age groups combined.

The agency has received reports that people who were vaccinated still developed laboratory-confirmed strains of flu. CDC officials said it’s not possible to know whether that’s happening more this season than usual and that the agency is “watching the situation closely.”

Overall, this year’s vaccines appear to be well matched for the two strains of influenza A and one strain of influenza B that are circulating this year, CDC officials have said.

The dominant strain this year is the H3N2 strain, which can cause more serious illness. Flu seasons can vary widely, but some years are severe, with hospitalizations of up to 200,000 people and between 3,000 and 49,000 deaths during a season.

As of December 14, the latest CDC figures available, about 127 million doses of flu vaccine had been distributed, from about 135 million doses produced for this season.