Modelling an avian influenza outbreak

The Public Library of Science has a study of the way in which avian influenza could spread globally, in the event that the limited human-to-human transmission becomes a pandemic.


It is important to note that the H5N1 pandemic may never occur, although as Treebeard the Ent would say in the Lord of the Rings: "Never is too long a word even for me."

It is also important to add the usual caveats about mathematical models. For instance, the model used in the bird flu study assumes: "also does not consider variations in travel frequency between individuals or viral spread in rural areas." Now to just take my personal travel arrangements over the winter months: I've been on eleven passenger aircraft in since early October, traveling to Egypt, four U.S. cities and the U.K.. I have had several chest, throat and synus infections. I'm writing this posting from the lobby of a Columbus, Ohio hotel, but this time next week I am likely to have made another two flights and attend two weddings. The chances for spreading infection from a few hundred people like me are surely enough to distort the models.

That said, the important data from this study:
1) a vaccine is likely to take eight months to prepare from the moment the virus transmits rapidly from human-to-human;
2) strategies involving the deployment in early-affected regions or countries (if international co-operation doesn't break down, which would neither be surprising nor entirely blameworthy) of antivirals like Tamiflu (oseltamivir), should slow down the spread of the virus by up to a year.

On an individual basis, locate a secure supply of antivirals now. You can expect public health authorities to use whatever powers they have to grab private supplies if a pandemic is announced. Keep an eye on this link, the World Health Organization's pandemic alert bulletin. If it rises from 3 to 4, I shall buy an antiviral injection within the week.

Until then, I am keeping an eye out for new treatments and the spread of H5N1, but not worrying about it. Other than a few precautions if traveling to countries that are currently affected by bird flu, there is no cause for alarm at this time.

Here's the basic information I think anyone who wants to avoid catching the disease, or failing that to survive it needs to know.

First the basics. H5N1 is a strain of influenza which normally affects migratory birds. Recent mutations in the virus have made it capable of surviving for several days or even weeks in ducks. The reason the virus is mutating is that like all viruses, the genetic composition of H5N1 is liable to have irregularities as it multiplies. Some of these mutations are "unsuccessful": they die out and the "mainstream" carries on. The problem for people is that there is a possibility that one such mutation will be spreadable from person to person (peer-to-peer of a kind not even filesharers would like). Already, H5N1 strains exist that are especially comfortable in a human host, and the death rate is not getting better at this time.

I've been tracking bird flu for nearly two months now. Every morning I check the World Health Organization's alerts for the latest developments, I know where all the human cases have been, I also know what the indicators are that market traders and scientists alike are waiting for.

Since I started, the death toll has increased by about 20%, which isn't too bad: fewer than 100 people are confirmed dead from bird flu across the world since 2003. The bad news is that the mortality rate is deteriorating, from exactly 50% when I first looked in early January, to 54.1% now. Also, some countries (like India) have governments which belatedly think there may be people who died of bird flu and it wasn't realised at the time.

The only really good news so far is that although H5N1 will quite possibly kill you, if you are unfortunate enough to catch it, you can only catch it from a bird, and so far chickens (overwhelmingly the major source of human infection) don't catch the virus easily from migratory birds. So the death rate would go up if either chickens caught the disease easier, or if the disease mutated into a human-transmissible killer, or both. Since November 2005, the WHO has considered the the avian flu outbreak to be in a "category 3" status (out of 6). The reason for this is that large nmbers of people have not been confirmed as having caught the disease from other people. Even the first few confirmed human-to-human casualties would not necessarily justify raising the alert level, but you can expect share prices to crash if "category 4 " is reached, the problem being that there is presently no reason to supposed that categories 5 and 6 would not rapidly follow.

The big unknown for industrialised countries is whether the death rate will be lower in better nourished populations where people are quicker to get medical help. We don't really know if taking vitamin C doses will reduce the chances of contracting H5N1. We know that some treatments exist for the existing strand of H5N1, but we don't really know if these would work on the mutated form, or how well.

Chickens and eggs are the two most likely sources of human infection. If both are cooked before you come near them there is no reason to worry (at least I'm pretty sure, and I would trust that myself). However, if like me you like to buy free range eggs by opening the box and checking the contents for cracks then I reckon that's going to be suicidal if local chickens are infected and somehow the eggs got into the stores. For environmental sceptics there is the joy of knowing that battery hens are safe in their crowded and inhumane pens, their eggs will be the last to be infected. Better still, for party-poopers, the only "organic chickens" left in the UK will probably be pumped full of vaccines and antibiotics to keep them from catching H5N1 from a passing protected wildfowl.

Welcome to Outbreak H5N1.

I finally got tired of reading and listening to the platitudes from governments and ignorant reports from the mainstream media. Meanwhile people are catching avian ifluenza and, for the most part, dying of it.

This blog has five aims:

1) to give the basic background information that will allow the reader to understand the disease and its actual threat;

2) to bring the most reliable information about where the H5N1 outbreak has reached;

3) to seperate panic-mongering from legitimate concern: warning of real chances of infection;

4) to watch out for a cross-over mutation: the point where H5N1 becomes a human spreadable disease;

5) to propose the optimal (in practice) avoidance and counter-measures for individuals and families.