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Prevention

Meanwhile, H5N1 continues to advance around the globe. Whilst it remains a problem firmly rooted in Asia, its appearance in Turkey, Romania, and Croatia last year raises the possibility that birds migrating to Africa this winter will have taken it with them. The close proximity between people and animals in eastern African countries creates another ideal breeding ground for the virus. Surveillance and capability to respond immediately after the detection of an outbreak is insufficient. Surveillance is important because culling infected birds dramatically reduces the chance that humans will come into contact with the virus and, therefore, the opportunity for avian H5N1 to reassort with human influenza.
Governments have also begun stockpiling antiviral drugs, which can block replication of most influenza A viruses or prevent their release from infected cells. Individuals have even gone in search of antivirals. In October of last year, the Internet auction giant eBay removed all listings for one antiviral from its British site as bids spiralled to more than £100 for a single dose.
A more realistic means of coping with a pandemic is by vaccination. In the US, clinical trials are already under way to test vaccines against a strain of H5N1 made safe through a technique called “reverse genetics” (Refer Figure 5 - The Mechanics of Reverse Genetics). This involves stitching together DNA plasmids, each containing a single influenza gene. This way we can say to the nature “You can design your own virus; therefore you can design your own vaccine,” .
Such trials should help confirm the safety of vaccination and determine the dosage and the number of doses needed to achieve effective immunity. Hopefully, antibodies raised from this vaccine will recognise the surface antigens on a pandemic influenza, giving some protection as researchers rush to decode the sequence of a pandemic strain and manufacturers work overtime to produce a vaccine against it. Until we know what exact strain is going to occur and cause a pandemic, we really can't make and stockpile vaccines.
So reverse genetics is also being used to try to second-guess the virus' next move and explore which reassorted viruses have what it takes to cause a pandemic. These experiments are based on the assumption that if avian H5N1 reassorts with a human influenza, it will most likely do so with human H3N2. Virologists at the US Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, are mixing genes from these two strains to find out which combinations are capable of infecting mammalian cells and hence pose a threat to humans.
This approach is useful for determining the virulence and pathogenicity of different hypothetical reassortant strains. I am carrying out similar experiments working with another threatening avian subtype—H7N7—rather than H5N1. However, it must be noted out, there is no way of finding out how efficiently these lab-confined strains will pass from human to human. We will learn this only once a pandemic is under way.


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