NEW YORK -- As the holiday season continues, the U.S. is also entering peak flu season. According to the Centers for Disease Control and Prevention, up to 650,000 people worldwide could die from complications of the flu.

Earlier this month, 3-year-old Rami Ibrahim had a flare up of asthma, but he didn't improve with treatment.

"He had a minor cough but he thought it was his asthma," said his mother, Dania Shaban. "So it wasn't anything that was shouting out this is the flu for him."

The diagnosis was flu, and the virus was attacking his lungs, causing him to spend a week in intensive care.

"He was sedated, he had a tube down his throat, he had a tube in his nose, he had three or four IVs," said Shaban.

It's very early in the flu season but it's shaping up to be a nasty one. Texas is one of 23 states already seeing high flu activity, more than double the number from the week before.

Dr. Mary Healy is an infectious disease expert at Texas Children's Hospital.

Dania Shaban and Rami Ibrahim CBS News

"We've had more positive tests over the last couple weeks," said Healy. "So it looks like we're really starting to get into the season in earnest and that certainly seems to be the trend nationally as well."

What concerns experts is the flu season that just concluded in Australia, which sometimes can preview the season here.

Australia had its most severe flu season in five years, and the vaccine used there is the same one used here. It's believed that one of the strains covered, called H3N2, mutated, making the vaccine only 10 percent effective.

"If you look at the CDC data, we don't have evidence that the virus has changed significantly," said Healy. "Hopefully we're not going to face the same situation."

Dr. Healy, infectious disease expert at Texas Children's Hospital CBS News

A vaccine takes months to make and scientists are looking at new ways of making it so when the virus mutates, they can quickly make a new one. In the meantime, the CDC recommends getting immunized, even if it only may provide a relatively small amount of protection.