Tamiflu-Resistant Flu Outbreak Reported in Australia, WHO Says

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Tamiflu-Resistant Flu Outbreak Reported in Australia's Newcastle, WHO Says By

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More than two dozen cases of H1N1 swine flu resistant to Roche Holding AG

(ROG)'s Tamiflu pill were reported in Australia in the largest outbreak of the

drug- evading influenza strain.

Viruses from 25 of 184 patients in the Newcastle area of eastern Australia

infected with the pandemic germ had a genetic mutation that reduces the potency

of Tamiflu, scientists said in a report distributed today by the International

Society for Infectious Diseases' ProMED-mail program.

The cases, first reported in May, raise concern that the resistant strain may

spread, leaving doctors without their preferred treatment for influenza.

GlaxoKline Plc (GSK)'s Relenza drug is effective against the mutant strain,

which is still found in the Newcastle area, according to the World Health

Organization's Collaborating Centre for Influenza in Melbourne.

" As long as it's isolated to Newcastle and that region, it's not so much of a

problem, " said Ian Barr, the center's deputy director, in a telephone interview

today. " If it spreads further, it might be a concern. Fortunately, we're heading

toward the end of our flu season. "

The cluster of cases with the mutant virus is the largest reported outbreak

globally to date, and shows the new variant is capable of being transmitted

efficiently in the absence of drug pressure, said McKimm-Breschkin, a

virologist at the Commonwealth Science and Industrial Research Organization in

Melbourne, who studies antiviral resistance.

`Fit and Transmissible'

" It's clearly fit and transmissible, " she said in a telephone interview today.

" It would be concerning having seen such a large cluster like that. "

None of those infected had taken Tamiflu prior to being tested for flu. Of 16

patients interviewed by the scientists, none had a history of immune

suppression, which contributes to drug resistance. None of the patients was

admitted to an intensive care unit or died from the infection, the report said.

Further interviews with cases and virological analyses are ongoing, the

scientists said.

The H1N1 virus that emerged in 2009 known as swine flu was reported in more than

214 countries and caused about 18,450 deaths worldwide through August 2010, when

the WHO declared an end to the pandemic. It's since become one of three seasonal

flu strains circulating worldwide, causing infections mostly during the winter

months.

Sporadic Resistance

Studies have shown that Tamiflu-resistant bugs develop sporadically in 0.4

percent to 4 percent of adults and children treated for seasonal influenza,

according to Basel, Switzerland- based Roche.

The outbreak of resistant H1N1 in Newcastle probably emerged in a treated

patient who passed the infection onto others, McKimm-Breschkin said.

Ten to 15 percent of H1N1 infections in the Hunter Valley area of New South

Wales state, which includes Newcastle, are resistant to Tamiflu, WHO's Barr

said. The seasonal flu vaccine protects against the new flu variant, as well as

influenza type B, the main strain circulating in the Newcastle area, he said.

Tamiflu and Relenza, an inhaled powder, reduce the severity and the duration of

flu symptoms by 24 to 30 hours if treatment is started within the first two days

of illness, according to the companies. Both drugs work by blocking a protein on

the surface of influenza particles called neuraminidase, which allows the virus

to spread from infected cells to other cells.

Mutant H1N1 viruses evade Tamiflu through a single genetic change known as the

H275Y mutation which prevents the medicine from clinging to neuraminidase,

enabling the pathogen to spread.

An outbreak of cases of seasonal flu with the H275Y mutation was first recorded

by Norway in January 2008 and by the following August widespread resistance was

reported in 40 countries in Europe, North and South America, Africa, Asia and

Australia.

http://www.bloomberg.com/news/2011-08-25/tamiflu-resistant-flu-outbreak-reported\

-in-australia-s-newcastle-who-says.html