[health-vn] Swine flu science: Who's writing what on the virus

[Vern Weitzel]

http://www.scidev.net/en/news/swine-flu-science-who-s-writing-what-on-the-virus.html

Swine flu science: Who's writing what on the virus
Naomi Antony
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.

http://www.newscientist.com/article/dn17049-expert-analysis-mexican-swine-flu--the-story-so-far.html

Speaking to Science for an article on swine flu mutation,

http://sciencenow.sciencemag.org/cgi/content/full/2009/429/1

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.

http://www.newscientist.com/article/dn17069-multidrug-strategy-could-slow-pandemic-spread.html

One mystery is the virus's origins.

UK newspaper The Guardian reports that UN scientists are trying to determine

http://www.guardian.co.uk/world/2009/may/01/swine-flu-mexico-la-gloria-un

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,

http://news.bbc.co.uk/2/hi/health/8028371.stm

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 
spread.

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.