AFP - The World Health Organisation said Friday that a mutation had been found in samples of the swine flu virus taken following the first two deaths from the pandemic in Norway.
"The Norwegian Institute of Public Health has informed WHO of a mutation detected in three H1N1 viruses," the WHO said in a briefing note.
"The viruses were isolated from the first two fatal cases of pandemic influenza in the country and one patient with severe illness," it said, although it added that no further instances were found in tests.
"Norwegian scientists have analysed samples from more than 70 patients with clinical illness and no further instances of this mutation have been detected. This finding suggests that the mutation is not widespread in the country," the UN health agency said.
However, it also revealed that a similar mutation had been observed in Brazil, China, Japan, Mexico, Ukraine, and the United States, as early as April.
"The mutations appear to occur sporadically and spontaneously. To date, no links between the small number of patients infected with the mutated virus have been found and the mutation does not appear to spread," the statement
The WHO also underlined that there was no evidence of more infections or more deaths as a result, while the mutated virus remained sensitive to antiviral drugs used to treat severe flu, oseltamivir (Tamiflu) and zanamivir (Relenza).
"Studies show that currently available pandemic vaccines confer protection," it added, as mass vaccine campaigns were slowly gaining ground in the northern hemisphere amid signs of public skepticism in several European nations.
Scientists fear that mutations in flu viruses could cause more virulent and deadly pandemic flu. The global health watchdog reiterated a call for close monitoring.
The WHO was still assessing the significance of the latest observation, but it underlined that many such changes in the virus do not alter the illness it causes in patients.
"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," it added.