The U.S. has been hit with a particularly aggressive early flu season with widespread reports of the illness across the country, hospitalizing 2,257 people and leaving 18 children dead before the end of 2012.

And health officials say the numbers haven’t even peaked yet.

“I think we’re still accelerating,” Tom Skinner, a Center for Disease Control and Prevention spokesman, told reporters.

The latest figures from the CDC show 29 states and New York City reporting high levels of flu activity, up from 16 states and New York City just one week prior.

Overall, 41 states reported cases.

“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.”

During that flu season, Joe Lastinger’s daughter Emily, 3, died only five days after coming down with the flu in late January.

“That was the first really bad season for children in a while,” said Joe Lastinger, 40.

“For whatever reason that’s not well understood, it affected her and it killed her.”

In that season, illnesses peaked in early to mid-December, with flu-related pneumonia and deaths peaking in early January.

That season was considered a “moderately severe” season for flu, and ended in mid-February.

It’s still too early to tell how bad this year’s flu season will get.

The US has been hit with a particularly aggressive early flu season with widespread reports of the illness across the country

While the CDC is waiting for more time to pass before classifying the season, Google Flu Trends has already listed it as “intense” by monitoring flu activity around the world based on internet search terms.

And roughly 4% of users on Flu Near You, a real-time tracking tool gaining about 100 new participants per week, say they’re experiencing symptoms.

“That’s huge,” John Brownstein, an epidemiologist and assistant professor of pediatrics at Harvard Medical School and Children’s Hospital Boston, told NBC News.

“Last year, we never got near this.”

John Brownstein is one of the founders of Flu Near You, a project, coordinated by Children’s Hospital Boston, the Skoll Global Threats Fund and the American Public Health Association.

The project has been a great tool for generating immediate data about the ongoing flu season.

“It’s what we call <<nowcasting>>,” John Brownstein said.

“It’s a more up-to-date view.”

CDC data can be as much as two weeks behind real-time reports.

John Brownstein’s data shows cough is this year’s most frequently reported symptom at 19%, ahead of sore throat at 16%, fatigue at 15%, headache at 14%, body ache at 10%, and fever at 7%.

Three out of four people reporting flu symptoms had not been vaccinated.

While John Brownstein’s data is more immediate, he cautioned against using it as an accurate measure of vaccine’s effectiveness because of variables in reporting.

During the 2010-2011 flu season, the CDC reports vaccine’s were effective for about 60% for all age groups combined.

While there were then reports of vaccinated people developing laboratory-confirmed flu strains, CDC officials said it’s not yet possible to know if this year’s trends match up though they are “watching the situation closely”.

Those officials also noted that this year’s vaccines seem to be a good match for the two strains of influenza A and one of influenza B circulating.

The H3N2 strain is dominant this year, and it can cause more serious illnesses.

Flu seasons vary widely in severity with some year’s totaling up to 200,000 hospitalized and between 3,000 to 49,000 dead.

About 127 million doses of flu vaccine have been distributed this year from the 15 million doses produced for this season.

Do you have the flu? These are the symptoms to watch for:

According to data being gathered by Flu Near You, flu cases have increased dramatically over the last few weeks. Here are the season’s most-reported symptoms:

1. Cough – 19%

2. Sore throat – 16%

3. Fatigue – 15%

4. Headache – 14%

5. Body Ache – 10%

6. Fever – 7%