WHO says Tamiflu-resistant H1N1 "isolated case"

By Stephanie Nebehay and Laura MacInnis

GENEVA (Reuters) - The first H1N1 infection found to be resistant to the antiviral drug Tamiflu represents an isolated case with no current implications for public health, the World Health Organization (WHO) said on Tuesday.

The United Nations agency has declared a global pandemic is underway from the virus known as swine flu which has so far been treatable with Tamiflu, made by Roche.

WHO spokesman Dick Thompson said that the discovery of a patient in Denmark whose infection did not respond to the drug, revealed by the Swiss company and Danish officials on Monday, did not amplify the severity of the virus.

"This is an isolated case. At this time, there is no public health implication. But we must remain alert as the virus can change at any time and we must not be complacent," he told Reuters.

Officials say the patient is now well and no further contagion with the resistant virus was detected.

Resistance to Tamiflu has been previously documented in the deadly bird flu virus H5N1 and seasonal H1N1 flu, Thompson said.

"We need to monitor the virus (H1N1) continuously," he said, adding that the WHO's global influenza surveillance network linking laboratories in 97 countries would keep monitoring it.

"WHO is not changing its recommendations for the use of antivirals," Thompson added, referring to the global body's advice to its 193 member states.

The WHO has previously said that the H1N1 virus is sensitive to a class of antiviral drugs which includes Tamiflu, known generically as oseltamivir, and Relenza by GlaxoSmithKline, known generically as zanamivir.

Denmark's State Serum Institute said, when making the announcement on Monday, that it was expected that the strain would at some point show resistance to Tamiflu.

It said that while the patient was found to be infected with a virus strain that had mutated to a form resistant to Tamiflu, the alternative drug Relenza, which is inhaled, remained an effective treatment.

GLOBAL PANDEMIC

The WHO on June 11 raised its pandemic flu alert to its highest level of 6, signifying that the first influenza pandemic since 1968 was under way [ID:nLC321991]

Flu viruses mutate regularly and can develop resistance to drugs at any time.

The WHO has said Tamiflu was working against strains of the new H1N1 flu but some health experts have expressed concern that it might be less effective than Relenza, since there have been widespread reports in the past year of resistance to Tamiflu by seasonal H1N1 flu, a distant cousin of the new swine flu virus.