Swine Flu That Resists Tamiflu Is Harder to Spread, WHO Says

By Michelle Fay Cortez
Sept. 15
(Bloomberg) -- Swine flu that can resist treatment with Roche Holding AG’s Tamiflu is also harder to spread to other people, according to World Health Organization officials.
Almost two dozen people have developed swine flu infections that don’t respond to Tamiflu, a mainstay of therapy for the outbreak that began in April. The genetic mutation that helps the virus evade the drug also thwarts its transmission, so the infection isn’t passed on to other patients, said David Mercer, acting head of the communicable diseases unit of the WHO’s European region.
“It’s a very specific genetic mutation that causes resistance and reduces the transmissibility of the virus, so it’s not infectious,” Mercer said in an interview in Copenhagen, where the WHO’s European governing body met this week.
The findings may reassure public health officials worried that overuse of Tamiflu would render impotent one of the key weapons against the pandemic virus. Some countries, including the U.K., took an aggressive approach to controlling the outbreak when it first arrived at the end of April, giving Tamiflu to people who had come into contact with pandemic flu patients to slow the spread of the disease.
For patients with seasonal influenza that doesn’t respond to Tamiflu, the only treatment option is GlaxoSmithKline Plc’s inhaled drug Relenza. Reducing therapies for the pandemic outbreak, caused by a novel combination of avian, swine and human influenza, could be disastrous if the virus, formally known as H1N1, turns more deadly, Mercer said. Flu patients who are otherwise healthy and without serious complications shouldn’t get Tamiflu, he said.
Viruses Change
“Healthy patients with uncomplicated illness don’t need antivirals,” Mercer said. “Viruses do change and evolution is unpredictable. Seasonal influenza is almost entirely resistant. Overuse of Tamiflu could result in the same thing” for swine flu, he said.
The WHO has been too firm on its advice to not treat patients with uncomplicated infections, said Liam Donaldson, England’s chief medical officer. About 40 percent of deaths occur among previously healthy people, and treatment is most effective when given early, before it’s clear whether the infection is complicated, he said.
“Some people will die” if left untreated, Donaldson said. “To regard them as inevitable statistical occurrences doesn’t go down well. We have these antivirals and we know they can have an impact.”

52,000 Cases

There have been more than 52,000 confirmed cases across 48 countries in Europe, including at least 140 deaths, Mercer said. Almost 90 percent of the deaths occurred in the U.K., Spain and Israel, he said.
There have been 23 cases of resistance developing to Tamiflu, Mercer said. Twelve of them were healthy people who had encountered swine flu patients, and were given Tamiflu in an effort to prevent the infection from taking hold, he said. Four or five others were healthy patients who had mild infections.
“The good news is that the resistant strains haven’t been transmissible to others,” Mercer said. “It’s not infecting anyone else.”
To contact the reporter on this story: Michelle Fay Cortez in London at mcortez@bloomberg.net
Last Updated: September 15, 2009 11:00 EDT
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