Flu has killed at least 26 children in the US, the Centre for Disease Control and Prevention (CDC) has said.
The CDC said in a weekly update that high levels of flu related cases were reported in 46 states, Xinhua reported.
"It appears that we're right in the middle of flu season this year," CDC director Tom Frieden said.
"But it's too soon to say whether we've peaked," Frieden added.
According to CDC, the flu season in US lasts about 13 weeks on average and the country has already been through about seven weeks so far.
The predominant circulating strain this season is H3N2, which Frieden called "a nastier flu virus" than other flu viruses.
Hospitalisation rates among people aged 65 years and older "are rising sharply," going from 52 per 1,00,000 the previous week to 92.
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The last H3N2 season was in 2012-13 and the cumulative hospitalisation rate for older people by the end of that season reached 183 per 1,00,000.
"We wouldn't be surprised to see something similar happening this year," the CDC chief said.
Five children died from flu during the last full week, bringing the total flu deaths to 26 this season.