* Says mutation 'spontaneous', could cause serious disease
OSLO, Nov 20 (Reuters) - 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 statement.
Authorities added they had no reason to believe the mutation had any implication for the effect of flu vaccines or antiviral drugs made by groups such as Roche (ROG.VX), GlaxoSmithKline (GSK.L), Novartis (NOVN.VX) or AstraZeneca (AZN.L).
H1N1, a mixture of swine, bird and human viruses, has killed more than 7,000 people globally.
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 people infected by the mutated virus 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.
Source: http://www.reuters.com/article/rbssHealthcareNews/idUSLK66976820091120 
