| HONG KONG
HONG KONG Scientists have found that a strain
of the H5N1 bird flu virus circulating in Thailand is resistant
to the flu drug amantadine, and they called for rigorous study
of H5N1 strains to better treat human victims.
While the World Health Organization has long recommended
that Tamiflu be used as the first line of defense against H5N1,
it said last May that a "dual therapy" combining amantadine and
Tamiflu may be considered in case of an outbreak.
Yong Poovorawan, a medical professor at Chulalongkorn
University in Bangkok, said an H5N1 strain in the central part
of Thailand had become resistant to amantadine, casting more
doubt over its use to fight the disease .
"It would be very dangerous if we don't know the
sensitivity or resistance of the strain to amantadine and we
use amantadine (to treat people infected with this strain of
H5N1)," Yong said.
He urged more rigorous surveillance and study.
"If you follow any new strain you will know the genetic
changes, you analyze its molecular structure, make experiments
to see which drug it is sensitive to and find out which is the
best antiviral for any given strain," he said.
"It's like a jigsaw, we have to find the pieces and see the
Yong and his researchers came to the latest conclusion
after studying the molecular structure of the strain, which has
been circulating in Thailand, Cambodia and Vietnam since 2004.
"We need to conduct in vitro experiments," he said,
referring to experiments in a laboratory or other controlled
However, he could not say how effective a dual
Tamiflu-amantadine therapy may be as Thailand has not tried
administering such a treatment.
Their findings were published in the March issue of the
journal Emerging Infectious Diseases.
There are two H5N1 strains circulating in Thailand, one in
the northeast and the other in the central part of the country.
Yong identified the strain in the northeast province of
Nakhon Phanom as the Fujian-like strain, which an international
group of virologists said in October may start another wave of
H5N1 outbreaks in poultry in Southeast Asia and Eurasia.
The Fujian-like strain was first isolated in China's
southern Fujian province in 2005.
"The Nakhon Phanom strain is the same as the Fujian-like
strain...which is also in (the Chinese provinces of) Anhui and
Zhejiang, and Laos," Yong said.
"From the molecular structure, we would say it is sensitive
to Tamiflu and amantadine."
Although H5N1 mostly affects birds, the big concern is that
it could mutate into a disease that easily passes between
people, triggering a global pandemic.
The emergence of various strains of H5N1 is a matter of
deep concern because each one may respond differently to
different antiviral drugs and vaccines.
"If there are too many strains and they are very different,
we will not know the efficacy of the vaccines," Yong said.