Commentary
Spreading H1N1 Tamiflu Resistance in Australia?
Recombinomics Commentary 19:25
September 5, 2008
AN unexpected influenza strain has swept through Geelong and blown out waiting times at the hospital emergency department, Barwon Health says.
Barwon Health said reports of 20-hour waits in the hospital's ED were due to a "strain of influenza not covered by this year's vaccine".
"Consequently, the Geelong Hospital is experiencing a period of high demand and high acuity," the Barwon Health statement said.
Barwon Health could not confirm the strain's identity late yesterday, but said it caused respiratory problems, particularly among older people.
The above comments describe a flu outbreak in Australia. Since the influenza is said to not be covered by the current vaccine, it is likely an outbreak of H1N1. The vaccine for 2007/2008 northern hemisphere flu season mismatched all three targets. However, poor reference anti-sera failed to detect significant differences between Solomon Island/3, the H1N1 vaccine target, and Brisbane/59, the dominant H1N1 sub-clade outside of Asia. Consequently, the 2008 vaccine for the southern hemisphere had new targets for H3N2 and Influenza B, but the mismatched Solomon Island/3 target was used, extending the mismatch to another season.
As was easily seen by phylogenetic analysis, Solomon Island/3 (clade 2A) was not circulating in 2007/2008, and had been replaced by Brisbane/59 (clade 2B), which also had H274Y. The first 10 sequenced H1N1 isolates in Australia had H274Y, suggesting the Tamiflu resistance was widespread and likely to be present in the patients experiencing respiratory problems.
Similar respiratory problems were reported in Honduras recently, and H1N1 HA sequences recently released suggests that those isolates, as well as isolates from Guatemala, which were virtually identical, had H274Y in the NA sequence.
As was seen in the recent fatal case from the Netherlands, treatment of H274Y positive H1N1 with Tamiflu fails to reduce the viral load, which could create problems for immuno-compromised patients, leading to death.
More information on the recent outbreak in Australia would be useful.
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