Published Date: 2005-10-15 23:50:00
Subject: PRO/AH/EDR> Influenza viruses, drug resistance (04)
Archive Number: 20051015.2999
INFLUENZA VIRUSES, DRUG RESISTANCE (04)
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A ProMED-mail post
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Date: Fri 14 Oct 2005
From: ProMED-mail <promed@promedmail.org>
Sspource: BBC Radio News, Fri 14 Oct 2005 [edited]
<http://news.bbc.co.uk/1/hi/health/4343136.stm>
Viet Nam: Case of H5N1 Virus Drug Resistance
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[The journal "Nature" is making available online a paper by
Kawaoka and colleagues on "Drug Resistant H5N1 virus" before
print publication on 20 October 2005 in view of current
concern about avian flu (Nature 2005; 437:1108.
<http://www.nature.com/nature/journal/vaop/ncurrent/pdf/4371108a.pdf>).
It highlights the possibility that the current prophylactic
regimen for Tamiflu (oseltamivir) may have contributed to
the emergence of partial resistance to the drug in a
Vietnamese patient. See BBC News report below. - Mod.CP]
A Vietnamese patient has become partially resistant to the
antiviral drug experts plan to use to tackle a human bird
flu outbreak. The UK government has ordered 14.6m doses of
Tamiflu, but the Nature report suggests this may not be
effective enough if an outbreak does happen.
At present, H5N1 flu strain poses only a limited threat to
humans as it cannot spread easily between people. But
experts fear it soon might, and other drugs may be needed to
combat it. However British authorities said the study did
not obviate the need to stockpile Tamiflu.
It may be that using Tamiflu (oseltamivir) for too little
time or at too low a dose could contribute to the emergence
of resistant virus, Yoshihiro Kawaoka from the University of
Tokyo and colleagues say. "Further investigation is
necessary to determine the prevalence of
oseltamivir-resistant H5N1 viruses among patients treated
with this drug," they warn.
The Department of Health said Tamiflu was the
internationally agreed product of choice. "Our antiviral
strategy is kept under constant review," added a spokesman.
The 14 year old Vietnamese girl they describe had been given
the drug in February [2005] as a preventative measure.
Although she had not had any known direct contact with
infected poultry, she had been caring for her 21 year old
brother who was thought to have [contracted avian
influenza]. The virus detected in the girl resembled that
found in her brother. The girl recovered without any
problems, but her case raises the possibility that she could
have been infected by her brother, rather than directly by
birds.
Also, oseltamivir on its own may not be sufficient to fight
a potential H5N1 pandemic and other drugs from the same
family such as Relenza (zanamivir) may be needed too, say
the researchers. "Although our findings are based on a virus
from only a single patient, they raise the possibility that
it might be useful to stockpile zanamivir as well as
oseltamivir in the event of an H5N1 influenza pandemic,"
they said.
Professor Ian Jones, microbiologist at the University of
Reading, said: "It's worthwhile noting but it is not
unexpected." He said past studies had shown viruses could
become resistant to Tamiflu. He saidsuch resistant strains
appeared to be less able to cause harm than the original
virus, which was reassuring. "They don't grow as well so
whilst the mutation does arise there is no reason to suppose
that [the mutant] virus is going to be a very successful
infectious agent." He added that antiviral drugs did not
cure someone of the virus, but merely keep down the levels
of infection to allow the body to mount its own response. "I
don't think it obviates the need for stockpiling Tamiflu,
but I do agree that it might be useful to have Relenza as
well."
A spokeswoman from the Health Protection Agency said: "This
is an interesting and important scientific paper and we are
aware that resistance is an issue and we have global
surveillance. "But it does not mean that resistant viruses
will emerge and transmit effectively."
--
ProMED-mail
<promed@promedmail.org>
See Also
Influenza viruses, drug resistance (03) 20051007.2924Influenza viruses, drug resistance (02): RFI 20051001.2878
Influenza viruses, drug resistance 20050930.2863
Avian influenza, human - East Asia (120): Viet Nam
20050901.2589
Avian influenza, human - East Asia (80): Viet Nam
20050519.1380
Avian influenza, poultry - China: antiviral treatment
20050621.1740
2004
---
Avian influenza - Eastern Asia (93): WHO statement
20040716.1935
Avian influenza A (H5N1) virus, human vaccine prospects
20040125.0300
Avian influenza A (H5N1) virus, drug resistance
20040125.0298
2001
---
Influenza virus, neuraminidase inhibitor resistance (02)
20010928.2372
Influenza virus, neuraminidase inhibitor resistance
20010926.2350
..................cp/sh
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