Dutch authorities said a patient infected by a mutant strain of the swine flu virus had died.
Harald Wychgel, spokesman for the Dutch Institute for Health and the Environment, told AFP that there had been a "minor change in the virus to make it resistant to Tamiflu," a key treatment for influenza.
"The patient was already seriously ill and being treated for that. He was infected by the Mexican flu and developed a resistance to Tamiflu," Wychgel told AFP.
The Dutch ANP news agency said the man had died in hospital in the northern city of Groningen, adding that two more patients in the Netherlands had shown resistance to Tamiflu.
It is the fifth fatal case of mutated A(H1N1) flu in Europe, after two in France and two in Norway.
The World Health Organisation said last month that a similar mutation had been observed in Brazil, China, Japan, Mexico, where the swine flu pandemic began, Ukraine, and the United States, as early as April.
Italy also reported a non-fatal case on Monday.
"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," an earlier WHO statement said.
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).
Fears of deadly flu
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.
"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. - (Sapa/AFP, December 2009)