In November 2005 influenza vaccination hit the national headlines as GP surgeries around the UK ran out of vaccine to treat those most at risk - the elderly, infirm and very young.
This coincided with a media frenzy linking the outbreak of avian flu in South East Asia and the associated human deaths with an inevitable human influenza pandemic to rank alongside that of 1918, 'Spanish flu, which killed an estimated 4050 million worldwide.
Influenza is a virus infection that originated in birds ana crossea to numans wnen birds were first domesticated. A virus is a crude 'dirty bomb'.
Human cells have around 30,000 genes, the E.coli bacterium 4000, and an influenza virus about 10. It comes wrapped in its own protein coal and ll s inese proteins that allow it to bind to a host cells surface (protein) receptor from where it can either invade the cell or Inject geneuc material Into Il.
Because of this most viruses infect single species to bind proteins must recognise one another. Once inside the cell it usurps the cell's 'machinery' to copy itself, its genes and protein coat, replicating, before 'bursting' out and infecting new cells.
In this process the host cell is killed. The 'common' flu virus is of high virulence, casy transmission person to person, but low 'pathogenicity, causing only mild symptoms in fit, healthy people.
The influenza virus is an Orthomyxovirus whose genes contain single stranded RNA. Unlike a human cell, where gene replication of doublestranded DNA is monitored, checked and mistakes corrected, mistakes in copying the genes in this group of viruses go uncorrected, they mutate and very rapidly.
Anti-viral drugs
exist, but are
expensive, in
short supply, difficult to make,
protected by
patent and uncertain in outcome. Thus, at any time there are manv variant strains of the virus in existence
Mutation may make the virus less or more pathogenic. The flu vaccine in any year is an attenuated, weakened mixture of those viral strains in existence thought most likely to cause infecDON.
The vaccine enables the immune system to prepare its defences against the expected allack In orael to reper ll, offering protection to those deemed 'at risk'. Each year a new vaccine is manufactured to ensure continued protection.
The avian flu A virus is classed into 16 H and 9 N subtypes of which the H5 and H7 subtypes can, when circulating in poultry, rapidly mutate to be highly pathenogenic, causing multiple organ failure with mortality, death rate, approaching 100% within 48 hours of onset.
Migratory, wild waterfowl, particularly ducks, have long been considered to be a natural reservoir for all influenza A viruses, carrying them and spreading them to poultry with no apparent harm to themselves.
A strain of the HS subtype, H5N1 is now endemic and widespread in wildfowl and poultry populations across S.E. Asia and has been found in swans in Croatia, turkeys in Turkey and poultry and swans in Komania
The H5N1 virus mutates rapidly and has a propensity to acquire genes from viruses infecting other species - reas SUL LUCIL.
Laboratory studies have shown it is highly pathenogenic and has the potential to cause serious disease in humans. Birds that survive infection continue to excrete the virus, orally and in faeces, for 10 days facilitating its further spread.
An outbreak in Hong Kong in 1997 caused severe respiratory illness in 18 people, 6 of whom died. Only the culling of the entire poultry population prevented a possible pandemic. It also intects pigs.
Since 2003 the World Health Organisation has confirmed 138 human cases and 71 deaths; lung tissue