Leading article: The world must work together against this threat

Global co-operation will be crucial if swine flu becomes a pandemic

It is said that a lie can be halfway around the world before the truth has even got its boots on. Something similar might be said of a mutated flu virus. An outbreak of swine flu in Mexico in the past fortnight has already reached New York and New Zealand. And the public health authorities are still desperately scrambling to get to grips with this new threat to human life.

There is a grim irony to the fact that this new viral threat has emerged from the Americas. The World Health Organisation (WHO) and national governments have been on alert for much of the past decade for an outbreak of killer flu from Asia. The other irony is that swine flu is already proving more lethal than the H5N1 bird flu virus we have been taught to fear. It has claimed 81 lives in a matter of weeks, almost a third as many as have died of H5N1 in a decade. And, unlike bird flu, the ability of this virus to pass from human to human is not in doubt.

Mexico is in a state of lockdown. President Felipe Calderon has shut schools and assumed powers to isolate the infected. Church services and football matches have been cancelled. A majority of bars and restaurants in Mexico City have closed their doors. The WHO will make a decision this week on whether to recommend that people do not travel to Mexico (a measure used in the 2003 Sars epidemic in southern China).

Yet the effects of a travel bar might be insignificant given that the virus has probably already spread some distance beyond Mexico's borders. The fears of scientists about the ease of viral transmission in an age of mass air travel would appear to have been vindicated.

We should note that there is still some uncertainty about this new virus. In Mexico it has primarily affected young adults with strong immune systems. This is worryingly similar to the pattern seen in the 1918 flu pandemic. But in America it has affected mainly young children, and appears rather less virulent. It is possible that the severity of the disease in Mexico is due to the circulation of a second, unrelated virus there, and one that will prove less able to cross national borders. We must hope that is the case.

But while hoping for the best, we must plan for the worst. That is certainly the view of Margaret Chan of the WHO and also Professor Nick Phin of our own Health Protection Agency.

Thankfully, since governments and health authorities have been preparing so long for a lethal outbreak of avian flu, they should be relatively well placed to respond to this new challenge. It is vital that national governments exchange information on the location of outbreaks. The first swine flu death in Mexico occurred on 13 April, but mucus samples were not sent to the US Center for Diseases and Control until five days later. If this process had been quicker, there might have been a better chance of containing the outbreak.

The creation of a swine flu vaccine ought to be a common endeavour. But that will take time. Meanwhile, the best that governments can do is to channel stocks of antiviral medication such as Tamiflu to regions where they are most needed. These drugs are not a cure, but they can lesson the effects of this virus.

The crucial point is that we are all in this fight together. Crude national protectionism in the face of a flu pandemic will prove just as counter-productive as the restraint of trade in the face of global recession. Our best defence against the globalisation of disease is global co-operation.