(CNN) - The flu is on the rise in much of the country, according to the Centers for Disease Control and Prevention.
The agency said 19 states now have high levels of flu activity.
The number of children who have died because of the flu has hit double digits.
Allison Eagle Speaker, 6, a Native American and a Montana native, loved her big brother Matt and little sister. She died Dec. 1 of flu.
“She was a beautiful little girl,” said Crystal White Shield, Allison’s mother. “We were blessed with her life and we miss her dearly.”
The CDC said the situation is getting worse.
Across the country, 19 states are showing high levels of flu activity compared with nine states last week. Some 13 children have died from the flu this season.
Children are particularly vulnerable to H1N1, this year's predominant flu strain.
Allison's mother wants other parents to be watchful when their children have the flu.
Allison died less than 48 hours after first becoming ill.
"This illness hit her really hard and really fast. For it to just take her life, nothing prepares you for how fast it moves," Shield said.
While Allison had mild asthma, about half of children who die from the flu are otherwise healthy, according to the CDC.
Of the children who died last year, 80 percent had not received a flu shot.
With months of flu season still to go, it's not too late for children or adults to get vaccinated.
The CDC reports the flu season began in October and runs through May.