* 3 H1N1 cases found with potentially significant mutation
* Two cases found among first fatalities in Norway
* Says disease's mutation could cause more serious illness
* WHO says mutated virus sensitive to antivirals, vaccines
(Adds WHO statement in new paras 4-6; CDC comment paras 15-17)
OSLO, Nov 20 Norwegian health authorities said
on Friday they have discovered a potentially significant
mutation in the H1N1 influenza strain that could be responsible
for causing the severest symptoms among those infected.
"The mutation could be affecting the virus' ability to go
deeper into the respiratory system, thus causing more serious
illness," the Norwegian Institute of Public Health said in a
There was no reason to believe the mutation had any
implication for the effectiveness of flu vaccines or antiviral
drugs made by groups such as Roche ROG.VX, GlaxoSmithKline
(GSK.L), Novartis NOVN.VX and AstraZeneca (AZN.L), the
The World Health Organisation said that the mutation did not
appear to be widespread in Norway and the virus in its mutated
form remained sensitive to antivirals and pandemic vaccines.
A similar mutation had been detected in H1N1 viruses
circulating in several other countries, including China and the
United States, in severe as well as in some mild cases, it said.
"Although further investigation is under way, no evidence
currently suggests that these mutations are leading to an
unusual increase in the number of H1N1 infections or a greater
number of severe or fatal cases," the WHO said in a statement.
H1N1, a mixture of swine, bird and human viruses, has killed
at least 6,770 people globally, according to its latest update.
In Norway the mutation was found in the bodies of two people
killed by the virus and of one person made seriously ill. The
two infected by the mutated virus who died were among the first
fatalities from the H1N1 pandemic in Norway, the institute said.
It was unclear whether the mutated virus was transmitted
among humans, the health authorities said.
"Based on what we know so far, it doesn't seem like the
mutated virus is circulating in the population, but rather that
spontaneous changes have happened in the three patients,"
director Geir Stene Larsen at the public health institute said
in the statement.
Norway has seen relatively more fatalities in the flu
pandemic compared to the size of the population versus other
European countries, with 23 confirmed deaths.
Public health authorities have said this could be due to the
country being hit early in the pandemic's northern hemisphere
winter wave, before a mass vaccination programme got underway.
"Nevertheless, it is important to study if there's still
something about the Norwegian fatalities that separate us from
other countries, and that make us learn something that
strengthens our treatment of the seriously ill," director
Bjorn-Inge Larsen at the Norwegian Directorate of Health said.
Dr. Anne Schuchat of the U.S. Centers for Disease Control
and Prevention said, "This mutation has been seen sporadically."
She said it is sometimes seen in patients who have mild
"I think it is just too soon to say what this might mean
long term," Schuchat told reporters in a telephone briefing.
(Reporting by Richard Solem; Additional reporting by Stephanie
Nebehay in Geneva and Maggie Fox in Washington; Editing by
Matthew Jones and Louise Ireland)