A small but significant number of flu viruses resistant to
Tamiflu have been detected in more than a dozen European countries, the World
Health Organization said on Wednesday.
Data show that Roche Holding AG’s Tamiflu, also known as
oseltamivir, seem to not be effective in about 13 percent of H1N1 viruses, the
main flu strain causing illness this year.
“It’s and unexpected finding and a signal worth watching,”
flu expert Frederick G. Hayden at the World Health Organization said quoted by
the Associated Press.
Surveillance done in previous years showed that one percent
of flu viruses would be expected to be resistant to the drug.
The strain is resistant because of a single mutation. The
new strain, called H274Y gene mutation, does not cause more serious disease
than regular strains, and can respond to other antivirals. However, health
experts worry that Tamiflu may become useless if the resistance become
widespread.
“Clearly, this is of global concern, but it is not a global
problem now,” Dr. Hayden said.
Norwegian epidemiologists were the first to draw attention
to the problem last week because they have the highest rate of viruses
resistant to Tamiflu: 70 percent of tested strains have been resistant. Britain, Denmark,
and France
also reported low but significant percentages. Nearly 3 percent of tested flu
samples have been resistant in the United States.
“We don’t know right now if this is a trend on the upswing
or just a small blip,” Dr. Joseph Bresee, chief of epidemiology and prevention
at the United States’
Centers for Disease Control and Prevention, said.
In a teleconference lasting two hours on Tuesday organized
by the World Health Organization, the participants agreed to continue close
monitoring of patients who develop the new strain so they could determine the
frequency, transmission, and distribution of the mutant strain as well as its
virulence, Dr. Hayden informed.
“The oseltamivir resistance investigation is still in its
early stages. A more accurate picture will only emerge when many more specimens
have been tested and more epidemiological information is available,” European Centre
for Disease Prevention and Control’s Influenza Project Team wrote in a separate
report in Thursday’s Eurosurveillance.
Health experts also want to determine where the new mutation
came from and how it developed. Usually, resistant strains affects people who
have been treated with Tamiflu, but it does not seem to be the case here, as in
Japan, where Tamiflu use is the highest in the world, no resistant viruses have
been reported this year.
