The World Health Organization (WHO) said on Friday that it was assessing the public health significance of a mutation of the pandemic H1N1 virus detected in Norway and some other countries, Xinhua reporeted.
The Norwegian Institute of Public Health has informed the WHO of a mutation of the H1N1 flu virus detected in two patients who died and one with severe illness.
In addition to Norway, the mutation has also been observed in Brazil, China, Japan, Mexico, Ukraine and the United States, with the earliest detection occurring in April, the UN agency said in a statement.
"The significance of the mutation is being assessed by scientists in the WHO network of influenza laboratories," the statement said.
"Although further investigation is underway, 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.
According to the agency, the virus with this mutation remains sensitive to the antiviral drugs, oseltamivir and zanamivir, and studies show that currently available pandemic vaccines confer protection.
In addition, 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.
In a separate statement, the WHO said that the pandemic virus has thus far caused at least 6,770 deaths worldwide, of which more than 4,800 occurred in the Americas.