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INFLUENZA A (H1N1) VIRUS, OSELTAMIVIR RESISTANCE (06): SOUTHERN HEMISPHERE
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A ProMED-mail post
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International Society for Infectious Diseases
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Date: Mon 25 Aug 2008
Source: stuff.co.nz, New Zealand Press Association (NZPA) report [edited]
<http://www.stuff.co.nz/4667440a11.html>
Tamiflu [oseltamivir] resistant forms of the "ordinary" seasonal
influenza are rapidly spreading and the drug may be ineffective in
fighting the dominant flu strain in South Africa this winter
[2008-2009]. World Health Organisation (WHO) data show tests on 107
people in South Africa with the H1N1 strain, one of the 3 most common
flu viruses in humans, found all had a mutant [virus] resistant to
Tamiflu. Only one patient was taking Tamiflu at the time.
Tests on 788 samples taken from H1N1 flu patients in 12 countries,
mostly in the southern hemisphere, from 1 Apr to 20 Aug 2008 found
that 242, or 31 percent, had the H274Y mutation [in the neuraminidase
protein gene] associated with Tamiflu resistance, the WHO said.
Southern hemisphere incidence of the mutation in tests on the H1N1
virus ranged from 100 percent in South Africa to 13 percent in Chile,
compared with a resistance rate of 16 percent found in 7528 samples
tested from the last quarter of 2007 to [31 Mar 2008] in 34
countries, mostly in the northern hemisphere.
"What we're seeing is the [spread] of the resistance gene and the
distribution of it throughout the world," said Lance Jennings, a
clinical virologist with the Canterbury District Health Board [New
Zealand], who is chairman of the Asia-Pacific Advisory Committee on
Influenza. "We have a lot to learn about the molecular epidemiology
of influenza viruses." The Tamiflu-resistant form of flu has been
reported in 40 countries in Europe, North and South America, Africa,
Asia, and Australia since widespread resistance to the [drug] was
first reported to the WHO by Norway in January [2007].
Until bird flu vaccines are developed for the specific pandemic
influenza virus once it evolves and starts spreading, work likely to
take 3 months or more, Tamiflu and another retroviral treatment,
Relenza, are the main medical weapons to battle pandemic flu. Tamiflu
is being stockpiled by the WHO and governments around the world for
use in the event of a pandemic, and to treat the H5N1 avian flu
strain that has infected humans in 15 of the 60 countries to which it
has spread.
Last year [2007], Swedish researchers warned that sewage systems do
not break down Tamiflu, and that the drug was being discharged in
rivers and streams used by the waterfowl thought to be the main
carriers of avian flu. They urged doctors not to over-prescribe
Tamiflu to avoid creating resistance in avian flu carried by ducks.
If those viruses combined with other viruses that made humans sick
they could mutate into strains resistant to Tamiflu, they said early
in 2007.
Health Minister David Cunliffe said this year [2008] that 103 of the
1229 treatment courses of Tamiflu the Government had bought at a cost
of [USD] 300 000 had reached their expiry dates.
--
Communicated by:
ProMED-mail Rapporteur Mary Marshall
[Oseltamivir (brand name Tamiflu) is a medication that decreases the
spread of influenza A and B viruses. Neuraminidase is an enzyme that
enables the influenza virus to spread from infected cells to healthy
cells. Oseltamivir blocks the action of neuraminidase (that is,
Tamiflu is a neuraminidase inhibitor) thereby reducing the spread of
influenza. By preventing the spread of virus from cell to cell, the
symptoms and duration of influenza infection are reduced. On average,
oseltamivir reduces the duration of symptoms by one and a half days
if treatment is started within 48 hours after symptoms begin.
Thereafter it becomes less effective.
As far as is known Tamiflu-resistant influenza A virus does not
exhibit any enhanced or decreased virulence.
The final paragraph of the report above reveals a weakness inherent
in the strategy of maintaining stockpiles of Tamiflu to combat
seasonal and avian influenza; namely, the drug has a limited shelf
life. - Mod.CP]
[see also:
Influenza A (H1N1) virus, oseltamivir resistance (05): China (HK)
20080203.0438
Influenza A (H1N1) virus, oseltamivir resistance (04): CA, USA 20080202.0428
Influenza A (H1N1) virus, oseltamivir resistance (03): corr. 20080203.0430
Influenza A (H1N1) virus, oseltamivir resistance (03) 20080201.0399
Influenza A (H1N1) virus, oseltamivir resistance (02): Europe 20080129.0371
Influenza A (H1N1) virus, oseltamivir resistance - Norway 20080128.0361
2007
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Avian influenza, human (101): Indonesia, Tamiflu resistance 20070622.2021
Influenza B virus, neuraminidase inhibitor resistance 20070404.1143
Avian influenza, human (15): Egypt, drug resistance 20070119.0253
Avian influenza, human (15): Egypt, drug resistance 20070118.0238
2006
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Avian influenza, human (162): oseltamivir resistance 20061010.2907
2005
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Avian influenza, human - East Asia (203): Tamiflu resistance 20051222.3659
Influenza viruses, drug resistance (06) 20051016.3021
Influenza viruses, drug resistance (05) 20051015.3014
Influenza viruses, drug resistance (04) 20051015.2999
Influenza viruses, drug resistance (03) 20051007.2924
Influenza viruses, drug resistance (02): RFI 20051001.2878
Influenza viruses, drug resistance 20050930.2863
2004
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Avian influenza A (H5N1) virus, drug resistance (02) 20040127.0316
Avian influenza A (H5N1) virus, drug resistance 20040125.0298
2001
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Influenza virus, neuraminidase inhibitor resistance (02) 20010928.2372
Influenza virus, neuraminidase inhibitor resistance 20010926.2350]
........................................cp/mj/jw
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