How Will the World React to Pandemic

So it's now just a question of timing. Within a day or so the World Health Organisation will officially declare a pandemic of H1N1 swine flu.

The move to pandemic Phase 6 will be official confirmation that the H1N1 virus is here to stay and that it will continue to spread globally. It must be hoped that the world does not over-react.

It will probably be months before most of us come into contact with the virus, and when we do, the vast majority will experience mild flu symptoms. It is not an indication that the virus is becoming more virulent. If those messages can be effectively communicated to the public, it could prevent a lot of unnecessary alarm.

A key decision concerns vaccines. Several manufacturers now have an H1N1 seed virus strain, and will be doing safety and efficacy testing in the coming months. We don't know how well the virus will grow or how many doses people will need to be protected.

Given the moderate nature of H1N1 it would be inconceivable for the WHO to ask manufacturers to switch completely from production of seasonal flu to a pandemic vaccine.

More likely is that companies will try to do a bit of both. Several countries, including the UK, have contracts to provide enough doses to immunise their entire populations. But despite upscaling in production in recent years, there won't be enough jabs to go round globally.

The first bulk doses might be ready in the late autumn and would be earmarked for frontline emergency staff and those with chronic respiratory problems. It's possible that by the time an H1N1 vaccine is ready, the virus will already be spreading rapidly in the northern hemisphere. We will learn a lot from what happens in Australia and other southern hemisphere countries in the months ahead.

So are we over-reacting to swine flu? I don't believe so. Even a pandemic of mostly mild illness will still cause huge disruption to business and society during its peak because it mostly affects those of working and school age.

Although the vast majority of those infected get mild symptoms, a few get seriously ill. The WHO estimates that about half the 140 deaths so far have been in young people who were previously healthy.

We must also watch out for genetic reassortment - or drift - in the DNA of the virus which might make it more virulent in future. There's no sign of that yet but it's another reason why we should all take the pandemic seriously, without the need for panic.