The Italian Health Ministry reported the country's first case of a mutant form of swine flu on Monday.
The ministry said the variation of the A(H1N1) virus was identical to one reported in Norway on November 20. On Friday, France reported the death of two people infected by the same mutation.
The A(H1N1) variation was found three or four months ago in a patient in Monza, near Milan, Italian Deputy Health Minister Ferruccio Fazio said in comments reported by ANSA news agency.
"The Higher Institute of Health has examined around 100 strains (of the virus) found in recent months in patients from all over Italy and up to now the mutation has only been found in one patient," the ministry said in a statement.
"Italian data suggest that at the moment the mutation in question is not dominating serious and fatal cases of the virus. Furthermore, the mutation seems to be sporadic and does not appear to be spreading," the ministry said.
Vaccination and anti-viral treatments were still effective against the mutation, the ministry said.
"Only vaccination protects us from the virus, which is likely to become more dangerous with mutations," Fazio said.
The Italian health institute said it had found one case of resistance to the Tamiflu antiviral treatment.
This was an isolated case involving a patient who was already very ill, the institute said, and the resistant strain did not appear to be spreading.