#Pandemic Influenza – The Risks in 2012 – #Vaccines

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Vaccines, Pandemic Influenza, Pandemic Influenza - The Risks in 2012, The risks of Pandemic Influenza

The influenza virus is found naturally in man, pigs, birds and many other animals and can move between species. It is a very mobile virus and can rapidly change itself to produce new viruses to which there is no natural protection. However, the initial step towards a new virus becoming a pandemic in man is, obviously, for it to be able to infect man, this is the first warning signal but it needs to be able to spread from human to human to achieve pandemic status.

What are H and N ?

The influenza virus comes in many forms A/B/C etc but it is only the A type that causes pandemics in man. On the surface of the A virus are two antigens (proteins) called Haemagglutinin and Neuraminidase (H and N respectively). As the virus mutates these antigens change and are given numbers to reflect these changes hence H1N1 etc.

H1N1 Swine Flu

In 2009 a swine influenza virus (called H1N1) caused a pandemic, starting a human to human spread in Mexico with early indications of a high mortality. The WHO responded, a pandemic was declared, the world's vaccine manufacturers mobilised vaccine manufacture, and the virus spread rapidly around the world. Typically influenza impacts the older age groups and those with pre-existing diseases. H1N1, however, impacted on young adults and this was probably because older people had a cross sensitivity protection from exposure to H1N1 in the 1950/60s. The initial high mortality was not reflected as it spread globally, although fatalities occurred they were more isolated than in Mexico. The vaccine was taken up widely in the US but less enthusiastically in Europe. The virus continues to circulate and is causing cases on a worldwide basis, but the strain is part of the seasonal vaccine and there is widespread immunity in the general population.

H5N1 – Bird (Avian) Flu

The H5N1 virus was first identified in the US in a wild mallard duck and is found widely throughout bird populations in Asia. Samples taken from poultry markets in China have shown that it is widely spread in the whole poultry population. A recent outbreak in Hong Kong seagulls led to a cull of chickens following the report of the death of a man on mainland China. It has the ability to infect man but, currently, cannot be transmitted from man to man. Each case reported to date has occurred in those who directly handle live poultry. It is however a significantly pathogenic virus and has caused 345 deaths out of 584 cases (Feb 2012) as it causes a viral pneumonia.

There are a number of vaccines already prepared for H5N1 and approved under the pandemic influenza approval systems. These would proceed into production in the event that the virus mutates to human to human transmission.

Recently a team in Rotterdam have created a highly contagious strain of H5N1 in the laboratory. Five mutations were introduced into the H5N1 genome and this was then passed between ferrets for 10 passages. The resultant virus was highly contagious. There is now a wide spread debate about the experiment. Clearly if the detailed technology is published any terrorist group could create lethal viruses, however the scientific community sees this as a dramatic advance that could help the understanding of influenza to prevent future epidemics. The debate continues.

A (H3N2) v`

H3N2 is endemic in pigs in Asia. In the last 4 months CDC have received over 12 reports of an H3N2 virus that has a matrix gene from a 2009 pandemic H1N1 strain in the viral shell. This has been given the nomenclature A (H3N2) v. It appears to be able to spread from pig to man and man to man. The CDC has prepared a vaccine seed strain in case the strain spreads and HHS is preparing a clinical trial with vaccine from Sanofi Pasteur and Novartis. No vaccine has been ordered but the manufacturers have been given the working seeds. Some cross protection to H3N2 viruses circulating in the 1990s is expected. This has also been found in pigs in Hong Kong

Cases of an H1N1v have also been identified.

H3N8

An H3N8 virus has caused the deaths of several hundred harbour seals off the New England coast. It is of low infectivity to man but the public are being warned not to approach the dead seals.

H4N8

A report in Virology from Japan has described an H4N8 which was found in shorebirds that is lethal to mice.

H5N2

The H5N2 outbreak in South African ostrich farms has devastated the industry following the cull of 38K birds.

H6N5

This has been isolated from a wild bird in South Korea, although this was transmissible in ferrets it was not pathogenic in pigs or poultry.

H7N2

This has infected two people.

H7N3

This has infected three people.

H9N2

This has infected three people.

H10N7

This has infected three people.

What will be the next pandemic ?

The influenza virus passes regularly across species and is highly mutant changing its immunological appearance. Small changes cause the seasonal influenza, however a large change which allows the virus to pass from man to man causes an epidemic. It is impossible to predict which virus will case the epidemic and when. The WHO have a worldwide surveillance organisation which detects the earliest changes and minimises the time until an effective vaccine is made available. The only certainty is that there will be another pandemic and the next one may be much more aggressive than H1N1.

 

Dr Kevin Bryett

Course Director

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Comments

  1. Dr.Iraj Khalili

    Hope you are fine and doing well.I’m Director manager in Razi Vaccine & Serum Inst.We are going to make flu vaccine under WHO license.

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