WASHINGTON – The pandemic of H1N1 swine flu raised the death rate among children across Europe late last year but not adults, researchers reported on Thursday.

Early reports showed about a 28 percent rise in deaths among children aged 5 to 14 in eight countries, Anne Mazick of the Statens Serum Institut in Copenhagen, Denmark and colleagues found.

This added up to about 77 deaths above what would normally be seen in that age group in those months, they reported in the online journal Eurosurveillance.

Estimating deaths from influenza is tricky, as most people are never tested, deaths cannot always be linked to flu and the cases of death are not always clearly reported. "This estimate is probably conservative due to delay in reporting," the European researchers added.

Mazick and colleagues pooled data from Belgium, Denmark, Greece, the Hesse region of Germany, Malta, Netherlands, Sweden and Switzerland -- a population of 66.8 million people.

"Our preliminary data show that the mortality reported during the 2009 influenza pandemic did not reach levels normally seen during seasonal influenza epidemics," the researchers wrote.

But they found 77 extra deaths among the 5- to 14-year-olds above what would normally be seen during that time.

"The steep rise of deaths after week 41 coincided with widespread pandemic influenza activity in the participating countries," they wrote.

"An excess number of 77 deaths corresponds roughly to a 28 percent increase in mortality among children 5-14 years old coinciding with the pandemic."

In comparison, the United States, with 300 million people, has confirmed more than 300 child deaths from H1N1 and says there were likely far more. That is more than double the numbers seen during the annual seasonal flu epidemic.