The World Health Organisation (WHO) said on Tuesday it was studying whether some seasonal flu viruses may be resistant to Tamiflu, after a study showed high levels of resistance to the widely-used drug in parts of Europe.
A preliminary survey issued by the European Centre for Disease Control (ECDC) said on Monday that of 148 samples of influenza A virus isolated from 10 European countries during November and December, 19 showed signs of resistance to the drug made by Roche Holding Ag.
WHO, a U.N. agency, began a global risk assessment on Tuesday, contacting national influenza institutes and laboratories which help it track antiviral susceptibility.
Authorities in countries including Japan, where Tamiflu is widely prescribed for ordinary flu, reported that they had not seen any unusual resistance to Tamiflu, WHO expert Dr. Frederick Hayden said.
“Based on initial reports, it is not a global problem now but it is a global concern,” Hayden told Reuters.
Pending completion of its review, the WHO was not changing its recommendations that oseltamivir — the generic name for Tamiflu — is the first drug for treatment and prevention of both ordinary flu and human birdflu, he said.
“Right now there is no intention of changing the recommendations in terms of anti-viral use by WHO,” Hayden said. “We continue to monitor the situation.”
National public health authorities may take decisions based on their own assessments, he added.
Of 16 samples from Norway, 12 tested positive for resistance against Tamiflu, according to the ECDC study. This had led Norwegian authorities to notify their European Union partners and the WHO of the situation.
Three other antiviral drugs have been approved by regulators for flu — GlaxoSmithKline’s Relenza, and amantadine and rimantadine. But the WHO does not recommend using the latter two because seasonal flu viruses now resist them.
WHO spokesman Gregory Hartl said the body had been surprised to see such high levels of resistance to oseltamivir in the study, which focused on the A H1N1 viruses circulating this winter in Europe.
Overall, the study by the Stockholm-based centre showed nearly 13 percent of the samples tested positive for resistance, compared to traditionally low resistance to the drug of between zero and two percent for the seasonal virus, he said.
Roche said on Monday no doubts had been raised about Tamiflu’s power to combat any deadly bird flu pandemic.
Since it re-emerged in 2003, the H5N1 virus has killed 223 people, including 100 in Indonesia, among 357 people known to have contracted the disease worldwide, according to WHO.
Hayden said that nearly 90 percent of people with bird flu who did not take Tamiflu had died. This compared with a survival rate of nearly 50 percent among confirmed cases given the drug.
“This is a very substantial improvement in survival, which is clinically important but still incomplete,” he said.
A key variable for survival was patient delay in seeking treatment, according to the American expert.
(Additional reporting by Maggie Fox in Washington; Editing by Jon Boyle)
http://www.medscape.com/viewarticle/569424?src=mp
