Prevention of a Pandemic

 

Avian flu 2005: first let us get the facts straight: we are talking about three viruses, one of which does not yet exist.

  1. H5N1 Avian flu, which affects birds, and has infected about 167 poultry handlers so far, of whom more than 60% have died. You have to handle live poultry to catch it. It is still safe to eat bids from unaffected areas.
  2. Seasonal Influenza, which will reach the UK/EU around the end of January, and for which a vaccination exists
  3. A future H5N1 Influenza virus - the pandemic virus - which will emerge:
    EITHER from mutations in H5N1 avian to enable it to spread from human to human, ("antigenic drift")
    OR from viruses 1 and 2 combining (reassorting) in the bloodstream of a poultry farmer or other bird worker who manages to contract both Influenzand avian flu at the same time. ("antigenic shift")

As H5N1 has such a high mortality rate (i.e. high virulence) it is devoutly to be hoped that the emergent pandemic virus will lose some of its virulence if it mutates.

 

Defending ourselves

The 1918 flu virus killed 20-40 million people and left thousands crippled with Parkinson's disease. We need to take this risk seriously, and to put up multi-layered defences.

These are the defences available:

  1. Prevent the pandemic virus emerging
  2. Limit or slow the spread of the pandemic virus if/when it does emerge, using:
    2.1 airline cross-infection management
    2.2 transmission control techniques (isolation and handwashing)
    2.3 vaccination
  3. Treatment
    3.1 anti-viral chemotherapy (Tamiflu/Oseltamivir)
    3.2 Inhibiting the cytokine storm


Preventing the emergence of a pandemic virus

Limiting spread of H5N1 Avian

Wild bird migration may play a part in causing fresh outbreaks, but poultry trading also plays a part. In fact the outbreak in Suffolk in February 2007 may have been (this is written during the unfolding outbreak) due to eggs brought in from Hungary, since the strain of H5N1 is the same as that in Hungary, and the Suffolk farm has links with that country. The alternative explanation, that a small infected wild bird flew into the turkey factory through a vent, is rather improbable.

In May 2006 Dr Kennedy Shortridge, a virologist at the University of Hong Kong who has researched the H5N1 virus in China since it first killed humans in 1997, warned against blaming the spread of the deadly H5N1 virus on migratory birds. He told a conference in Singapore, organized by the Lancet medical journal, that the movement of poultry around the world could play a major role. Dr Shortridge advised researchers not to rush to blame migratory birds, but to look for the disease also along routes of human transportation, including by rail, road, and water. Source

The question of poultry workers

The WHO global influenza preparedness plan The role of WHO and recommendations for national measures before and during pandemics (WHO/CDS/CSR/GIP/2005.5) states that countries with cases should:

"... continue promoting vaccination with seasonal influenza vaccine to limit risk of dual infection in those most likely to be exposed to the animal virus, and potentially decrease concurrent circulation of human strains in the outbreak affected area."
http://whqlibdoc.who.int/hq/2005/WHO_CDS_CSR_GIP_2005.5.pdf p27


This tactic was used in the successful defeat to the H7N7 outbreak in 2003:
"People undertaking slaughter of infected chickens, pigs and turkeys have been vaccinated against human influenza virus and are also receiving antiviral drug treatment. The aim is not only to protect them against infection by the bird influenza virus, but also to avoid a new and more virulent virus being formed from mixing (reassortment) of human and avian influenza viruses in someone with co-infection of viruses."
http://www.pighealth.com/influenza3.htm

There is a limitation to this policy is in the shortage of influenza vaccines. Production of Fluvirin was lost for 3 months earlier this year. The annual production run is 300,000,000 doses. A full vaccination programme around trouble spots might need that output to be doubled or trebled. However, as pointed out above, time, although precious, is still on our side, and if WHO approved vaccine manufacturers could franchise production out to smaller companies, it is possible that demand could be met.

Up to the 25th January 2006 I was pressing for the WHO to apply this policy in order to prevent reassortment and emergence of the pandemic strain of H5N1. However, at that time I became aware of the work of Taubenburger, who showed that the 1918 strain emerged by antigenic drift, that is by working out how to spread from human to human without reassorting with human influenza virus. Moreover, the 1957 and 1968 pandemics, which were far milder, arose by reassortment "antigenic shift". We can infer from this that reassortment is the lesser of two evils, and it would be better to let reassortment take place, rather than to successfully block reassortment only for an antigenically drifted H5N1 to occupy the ecological niche with a more deadly pandemic.

All this is is based on reasoning rather than "scientific proof" (in fact proof does not happpen in science, only in mathematics), but the bottom line is that it would be unwise to try to block the reassortment.

In fact, the WHO policy is being adopted in such an half hearted manner that it is irrelevant.

Without the vaccination policy, emergence of the pandemic virus is very probable.

Limiting the spread via air travel

If we fail to immunise workers who have contact with the virus, and a new H5N1 strain does emerge, we can slow its global spread by monitoring air travellers.

If an outbreak occurs, air passengers from the infected area should be monitored. Infra red detectors to pick out people with raised core temperatures at airports have a place, but are imperfect since a person who is incubating the virus may be shedding it, but may not have a raised temperature. On the other hand, it would be feasible to change airliner cabin air filters at the end of each leg of the flight. PCR tests could identify aircraft with cabin air carrying the virus within hours. Passengers and crew from an infected flight would have to be quarantined if the virus is found.

A suitable machine to do this work can be found here.

In addition, hygiene standards in aircraft toilets should be vastly improved.

These measures are unlikely absolutely to contain the virus, but they will slow its global transmission, buying us valuable time to get a vaccine prepared and rolled out.

Please write to your democratic representative and ask them to put these measures in place.

 

Dealing with the pandemic

If, despite these barriers, a new strain of pandemic flu arrives in a country, isolation of cases will help to limit the percentage of the polulation is affected.

We need to press hard to get these measures in place. The professionals and experts have valuable advice to give, but they work in committees, which are a necessary way of making plans, but the weakness of committees lies in their tendency to follow the accepted line, and to be resistant to new ways of thinking. The proposals laid out in these pages are in addition to, not in opposition to, official advice.

Treatment

The anti viral drugs Oseltamivir (Tamiflu) and the amantidine derivatives may help to fight the virus, although the effectiveness of the older types is being lost due to the extremely foolish use of the antivirals in giving it to chickens. This is certain to encourage the virus to learn how to resist the drugs.

Pandemic influenza will probably kill by cytokine storm, a positive feedback loop weher defence cells overreact and swamp the virus infected lungs. There is a cheap, safe, long established drug which may be able to inhibit this reaction and offer hope of an affordable treatment. I have had this letter published in the on-line section of the BMJ.

 

 
© 2001 R. Lawson This page was last updated on 5.2.2007