New virus 'very unstable'
2009-05-12 18:25
Hong Kong - A leading virologist has
described the new H1N1 influenza virus as "very unstable",
meaning it could mix and swap genetic material when exposed to
other viruses.
The new virus, which has infected 5 251 people in 30
countries and killed 61, has displayed great efficiency in
spreading among people, said Guan Yi, a microbiologist with the
University of Hong Kong.
"This virus has been around only a few months, it is very
unstable ... and we know that its presence is dramatically
increasing in human population, so the chance of it meeting
with H5N1 is actually increased," Guan said in an interview on
Tuesday.
"Both H1N1 and H5N1 are unstable so the chances of them
exchanging genetic material are higher, whereas a stable
(seasonal flu) virus is less likely to take on genetic
material."
While H1N1 appears to be mild so far with many infected
people recovering even without treatment, the H5N1 has a
mortality rate of between 60 to 70%.
Experts are fearful about the emergence of a hybrid which
combines the killing power of the H5N1 with the efficient
transmissibility of H1N1.
H5N1 is believed to be endemic in
countries like China, Indonesia, Vietnam and Egypt.
New H1N1 virus strain
Guan, an expert on both the H5N1 and Sars, has analysed the
genetic sequences of the new virus, which is a triple
reassortant containing genetic material from swine, human and
bird.
He said there was a huge information gap due to a lack of
regular surveillance on animal disease.
Each one of the eight gene segments in the new virus has
been seen in pigs in the past 10 years, but experts have no
clue when this new H1N1 virus strain first appeared and in
which animal species it had been incubating, Guan said.
"We know when each gene segment appeared, but we don't know
when this strain first appeared, there is an information gap of
about five to 10 years, from 1999 to 2009. If there was regular
surveillance, we would know when this virus came about," he
said.
"We don't know if this reassortment happened in pigs or
human ... It's likely to have come from pigs because all the
segments have been found in pigs, but we can't be 100%
sure."
'Fighting for time'
Guan backed stringent moves taken by some governments to
keep the virus at bay, such as quarantining.
"They are useful because we are now fighting for time to
develop vaccines and antivirals, which will then minimise its
impact on people (over the longer term)," he said.
"Already it appears to more virulent than seasonal flu
because it is killing younger people and it appears to have
higher mortality than seasonal flu, so it doesn't make sense to
treat this like seasonal flu."
Seasonal flu kills about 250 000 to 500 000 people annually
with a fatality rate of less than 0.1%.
A study published in Science on Monday estimated that the
new H1N1 flu virus has a case fatality ratio of 0.4%
based on confirmed and suspected deaths.