The latest outbreak of foot and mouth (FMD) could turn out to be a watershed for the way we handle these events.

The government’s response so far has been good. It has stopped all animal movements immediately in a way that did not happen in 2001 and it is acting fast to diagnose the strain of the virus.

However, the animals on this farm have been infected for at least a week and there is a risk this will become an epidemic. If that happens then the government will have to decide on slaughter or vaccination.

This is not a matter of science. It is a social and cultural issue. In 2001 people were very distressed at the slaughter of animals in such large numbers. It is no longer acceptable to kill millions of animals.

But vaccination is not a simple choice. It upsets international trade because there is a waiting period of months to see if it has worked.

It also disrupts farming. A vaccinated animal is protected against developing symptoms but may be a carrier — so such animals cannot be moved.

In Britain there is a history of refusing to put vaccinated animals into the food chain — even though they are perfectly edible. We need to resolve these issues.

What this illustrates is that FMD is not a simple disease. Outbreaks like these cause very different responses around the world.

In Africa, Asia, India and South America FMD is endemic. They have come to live with the disease. But in Europe, Australasia and North America the response has always been to wipe it out.

Why is this? The first thing to ask is why FMD is important at all? After all, it is not lethal except to young animals and it does not infect humans.

The answer is that it has a huge economic impact on farming because it cuts back productive capacity. It is a debilitating disease that stops animals converting food into meat and milk. That is why it has a much bigger effect in countries with intensive farming.

The other reason we slaughter animals is because, in island countries, it works. We can keep the virus out.

Other parts of Europe and the rest of the world cannot take that approach. They have it endemically or it comes over their land borders. That is why they use vaccination. They wage an ongoing battle to keep it down to a minimal level.

The low point for infection was about 25 years ago, but globalisation has put that trend into reverse. As the threat grows, we will have to rethink our resistance to vaccination.

Sir Brian Follett was chairman of the Royal Society inquiry into livestock diseases that followed the 2001 FMD outbreak

The science

What is foot and mouth? A highly infectious viral disease of cloven-hooved animals such as pigs, sheep, cattle and goats. There are seven strains.

What does it do? Animals can carry and spread the virus for up to two days before they show symptoms. The first signs are a fever followed by the development of blisters, mostly in the mouth and on the feet. Most adult animals survive.

Why slaughter them? Besides removing the risk of the disease spreading, the virus leaves animals badly weakened, unable to produce economic amounts of milk.

How does it spread? It is found in fluid from blisters and also in saliva, milk and dung. It can spread miles in the wind. Livestock pick up the virus by direct contact with an infected animal or with contaminated foodstuffs.

Can people contract it? There has been only one recorded case in the UK, in 1966; leaving blisters and flu-like symptoms.

How long can the disease survive? Heat, sunlight and disinfectants can destroy the virus within hours, but in darkness it can stay alive for months.

What happens to infected animals? British policy is the mandatory slaughter of affected animals and all livestock in contact with them. Now the government is prepared to vaccinate apparently uninfected animals after rejecting it in 2001.

How is it contained? With a 1.8mile restriction zone around the infected area and a national ban on the movement of sheep, cattle and pigs.

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