Bird flu

We don't hear much about bird flu - possibly better called poultry flu - these days.  A few years ago the media were full of it and how it might threaten the poultry industry here in the UK and elsewhere and the grave dangers of the disease jumping the species barrier and becoming a human pandemic.  Well it hasn't happened yet.  Let's hope it never does.

Nowadays we are more concerned about so-called swine flu which has led to thousands of human deaths across the world this year alone.

But bird flu, avian influenza, highly pathogenic H5N1 virus, has dropped out of the news and out of most of our thinking.

H5N1 first arrived  - as far as we know - in the UK in April 2006 on the Fife coast at Cellardyke.  The virus was detected in an already-dead swan.  I couldn't identify a virus but the authorities were embarrassed that they couldn't identify a swan - it was first said to be a mute swan but later a whooper swan.  A mess-up that has for me always epitomised the lack of attention paid to the details of the involvement of wild birds in the spread of this disease.

The next outbreak was in eastern England, in Suffolk, at a farm at Upper Holton in February 2007.  The official epidemiological review of the case found that import of turkey meat to this site from Hungary (where there had been a recent outbreak) was the most likely source of infection - although news of the meat imports was slow to emerge from the company involved or Defra whilst speculation about the role of wild birds in disease transmission was rife.

The next autumn brought another East Anglian outbreak, this time near Diss, in November 2007. Despite the fact that no H5N1 was found in wild birds in the vicinity the final epidemiology report leant towards wild birds being the source of the outbreak because there was an ornamental lake with wild birds nearby!

The next and last UK H5N1 outbreak was in wild birds in Dorset at the Abbotsbury swannery in January 2008. Only wild birds were affected this time and the virus was detected in a number of mute swans and a Canada goose.  This site holds large numbers of semi-domesticated but wild and free-flying mute swans as well as the usual mix of gulls and migrant ducks that might be found in many places in the UK.   One would have to say that the Abbotsbury swannery is unique in the UK and although the swans are wild, in that they can come and go as they like, it is closer to a free-range swan zoo than any other site in the UK.  If you were a mute swan trying to catch or hand on a disease to another mute swan then this might be your location of choice.  Having said that, the virus was only picked up and detected because of routine monitoring that had been put in place because of fears over the H5N1 virus.  There was no mass death of swans - similar numbers died as usual but the routine testing detected the virus in some of them.  So, if we hadn't been looking very hard for the virus no-one would have noticed anything unusual.

After this 'outbreak' it seemed quite likely that the H5N1 virus was floating around in wild bird populations and might be brought to the UK by migratory waterfowl such as ducks, geese, swans and gulls each winter - perhaps particularly winters with cold weather affecting much of Europe where larger than usual numbers of such birds were pushed towards the Uk to escape Arctic conditions on continental Europe.

And it is the recent cold weather, there is still a little ice and snow outside my house today, that made me remember bird flu.  The UK has been officially free of H5N1 since November 2008 although monitoring continues.  That means that through all of the 2008/09 winter, and so far through this one too, there have been no H5N1 cases in the UK.  That is despite the annual movement in and out of the country of millions of wild birds each winter.  It's tempting to think that bird flu has fizzled out or was a flash in the pan. 

I'd say it is far too early to be sure that we don't need to worry too much about bird flu but this prompted me to look at the number of human deaths across the world from H5N1. I don't know how these data are compiled so can't speak at all authoritatively on them but it is striking that the number of human deaths across the world now stands at 263 and that they appeared to peak in 2006.  Indonesia has suffered, and perhaps admitted, more deaths than any other country; the number of cases in China seems surpisingly low; Egypt appears to be the 2009 hotspot; the one human case and death in Nigeria seems way out of step with all the others; there are no European human deaths.

So far, so good one might say, taking a global perspective.  There are somewhere between one and two human deaths, from all causes, per second across the world - about 125,000 a day. So the killing rate of bird flu is pretty low in the big scheme of things.  Any man's death diminishes me, for I am involved in mankind, but 263 reported human deaths, so far, is a long way, so far, from the high-profile predictions of a human bird flu pandemic killing millions or billions of people.  Let's be thankful for that - and remain vigilant.

There are three thoughts that I take from all this.

First, we seem, as a species, incredibly keen to predict our own demise from novel diseases and there is a terrible danger of crying wolf.  SARS, bird flu and now swine flu have all killed people, and killed people across many countries of the world, but their collective killing power is tiny (so far) compared with the less than novel causes of death including road traffic accidents, heart disease and almost any cause of death you could name. 

Second, we seem, as a species, incredibly keen to pin the blame on 'wildlife' every time a disease affects our livestock.  Briefly in the 2001 foot and mouth outbreak in the UK there were calls to cull crows and other birds - nonsense in terms of an effective strategy and we learned soon afterwards that widespread livestock transport was an issue that we had to look at much more carefully.  With bird flu there was amazing reluctance to admit publicly that partly-processed turkey meat was being regularly transported from a country with a recent bird flu outbreak (Hungary) to the very site where bird flu had broken out in Suffolk.   A more realistic approach will be to recognise that diseases that affect domestic livestock are likely to be shared with wildlife - and that the diseases have the potential to pass from one to the other in either direction.  Mitigating risk will need to look at livestock and wildlife together - and the movements of both.  And we may be able to do much more about livestock housing conditions than we can about the movements about wild species.

Third, I just have a feeling that the worries, probably well-meaning and possibly well-founded, expressed about the seriousness of the impact of H5N1 on human mortality, not yet realised (and let us hope they never will be), have done some harm to the standing of science as a whole.  When scientists warn of danger and the worst fears do not come to pass then the public, I suspect, downgrades the next threat.  Perhaps a bigger dose of bird flu would have allowed us to respond better to the climate change threat?  Maybe that's fanciful.