WASHINGTON, USA - US officials Friday said infections from A(H1N1) virus had slowed in the United States this week, raising hopes the early roll-out of vaccines may be bringing the disease under control.

"We are beginning to see some decline in influenza activity around the country, but there is still a lot of influenza everywhere," said Anne Schuchat, from the US Centers for Disease Control.

"We are still seeing a lot of influenza around the country, but we are seeing increasing amount of vaccines.

"Forty-three states are reporting widespread activity that is down from 46 last week but it is still much greater that we have ever seen at this time of year."

But despite the figures, the death toll continued to mount.

"This past week 21 influenza associated pediatric deaths were reported to us, 15 of those were confirmed to be due to H1N1."

And with months to go in the normal flu season -- December to May -- experts are braced for more bad news.

"We may have weeks and months of a lot of disease ahead of us," said Schuchat, who is head of the CDC's National Center for Immunization and Respiratory Diseases.

The authorities are still struggling to meet that challenge with an adequate supply of vaccine, she added.

"Supply of vaccines continues to increase, we are not where we want to be, but available vaccine is being quickly ordered and shipped and we are in better shape today than a couple weeks ago."

Schuchat's comments come as the World Health Organization reported that a mutation of the virus had been found in Norway.

The body stressed the mutation did not appear to cause a more contagious or more dangerous form of A(H1N1) influenza and that some similar cases observed elsewhere had been mild.