[health-vn] Swine flu science: Who's writing what on the virus
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Thu May 7 14:33:30 EST 2009
Swine flu science: Who's writing what on the virus
1 May 2009 | EN | ES | 中文
Influenza A(H1N1): negative stain EM image of the virus
C. S. Goldsmith and A. Balish, CDC
As swine flu spreads around the globe, scientists are seeking to build their
understanding of the virus — particularly the likelihood that it will mutate.
From the wealth of information in the media, SciDev.Net has selected some of
the best articles considering the science behind swine flu.
According to Wendy Barclay — professor of influenza virology at the UK-based
Imperial College London — swine flu, now known as A(H1N1), is a 'triple
reassortment' virus. It is made up of segments from human, swine and avian
viruses, Barclay told New Scientist in an expert analysis.
Speaking to Science for an article on swine flu mutation,
Kennedy Shortridge — a virologist at the University of Hong Kong — warned that
as the virus spreads further this mixture is likely to increase: "… the farther
the virus spreads, the more chance it will mix, or reassort, with other flu
viruses in circulation and turn into something more lethal".
He said that there are human strains of the virus in areas that are resistant to
the current treatment Tamiflu and urged the sequencing of as many viral samples
as possible to help predict changes in the virus.
In an attempt to predict the virus's spread, Ira Longini and colleagues at the
US-based University of Washington are trying to acquire as much data as possible
on the virus's basic reproductive number, R0, a variable that reveals the number
of new infections caused by each infected person. Longini told Science in the
same article that this is the key factor in determining the virus's spread.
Scientists are also eager to find out "whether a virus must mutate to move from
pigs to humans and whether, as is the case with bird flu in humans, a specific
mutation makes it more virulent," Science reports.
A strategy to postpone the emergence of resistance is to "hold off using your
primary drug until the cumulative number of cases reaches a sufficiently high
number," says Joseph Wu of the University of Hong Kong. He told New Scientist
that stockpiling just one drug would encourage resistance.
One mystery is the virus's origins.
UK newspaper The Guardian reports that UN scientists are trying to determine
whether La Gloria, Mexico, is the virus's source. The village is suspected
because samples acquired from a five-year-old there provide the earliest
confirmed case of the disease. Other theories include migrant workers bringing
the virus to Mexico from California, or that the earliest source is a
39-year-old woman in the southern Mexican state of Oaxaca.
Scientists are also investigating why sufferers outside Mexico have experienced
comparatively mild symptoms, Barclay told New Scientist. As yet there is no
evidence that the genetic makeup of the Mexican strains differ from those in the
United States, for example, says Barclay.
BBC Online reports that preliminary analysis of the virus suggests that it is "a
fairly mild strain". In a summary of what is known about swine flu,
scientists say further mutation is required to cause mass deaths, but future
evolution of the virus remains unknown. UK scientists will begin work today (1
May) on samples of the virus sent from the US. The research is essential in
order to work out the structure of the virus, its origins and its propensity to
Barclay told BBC Online that "initial indications suggest there is nothing about
the genetic makeup of the new virus which is a cause for particular concern".
Preliminary "guesswork" has found that H1N1 attaches itself to the upper
respiratory tract, spreading easily via coughing and sneezing but causing only
mild infection. This is unlike the H5N1 avian influenza virus, which binds
further down in the lungs and causes more severe illness, even though human
transmission is rare.
But it will take "weeks and months of biological analysis" to fully determine
H1N1's potential, reports BBC Online.
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