Influenza Update
WHO responds to reports of patient-to-patient spread of Tamiflu-resistant
H1N1 virus
Media reports in November
noted that Tamiflu resistant
swine flu had spread between
patients in a hospital ward.
The BBC reported that “a
total of five patients on a unit
treating people with severe
underlying health conditions
at the University Hospital of
Wales, Cardiff were infected.
Of those, three appear to have
acquired the infection in
hospital.
“They are thought to be the
first confirmed cases of
person-to-person transmission
of a Tamiflu-resistant strain in
the world. There have been
several dozen reports around
the world of people developing
resistance to Tamiflu
while taking the drug, but
they have not passed on the
strain to others.”
In a media briefing on 26
November Dr Keiji Fukuda,
Special Adviser to the
Director-General on Pandemic
Influenza, World Health Organisation, responded to
these reports.
“There have been two separate
clusters of oseltamivir
resistance identified in the
UK and in the United States.
In the United Kingdom there
were nine patients in a
hospital who developed
pandemic illness and from five
of these patients, oseltamivir
resistant viruses were identified,”
Dr Fukuda said.
“In a separate cluster in the
United States there were four
patients in one hospital who
also developed pandemic
illness while hospitalised.”
According to the WHO, all
the resistant viruses carried
the same H275Y mutation,
indicating resistance to oseltamivir, but susceptibility
to the second antiviral drug,
zanamivir.
Dr Fukuda said these people
were in immuno-compromised
conditions either because of
their underlying disease – some of which were hematologic
malignancies – or
because of treatment for their
disease.
In a statement issued 2
December, the WHO said the
emergence of drug-resistant
influenza viruses in severely immunosuppressed or
immunocompromised patients
undergoing antiviral treatment
is not unexpected and
has been well documented
during seasonal influenza.
The WHO added the
outbreaks are being further
investigated to determine the
mode of transmission within
the wards. No illness in staff
caring for these patients has
been detected.
Zanamivir
The WHO pointed out that
once oseltamivir resistant
virus has been detected in a
ward treating severely
immunocompromised
patients, doctors should
consider switching to
zanamivir as the antiviral drug
of first choice for treatment,
and when considering post
exposure prophylactic treatment
of other patients on the
ward. 
Date
of upload: 26th Jan 2010
