It was always a case of when rather than if bird flu came to the UK. But the outbreak at a Suffolk farm has come as a surprise.
Defra is hoping the infection is a one-off
Migrating birds do not come to the UK for a month or two. So the priority for government scientists is to trace how the virus got here.
The most likely explanation is that it was from a wild bird arriving earlier than expected.
However, other possible sources, such as farm supplies, have to be ruled out to ensure that the disease does not spread further.
Scientists are trying to determine whether or not the virus is the same virulent strain of H5N1 that has killed birds in Asia, or a milder form. That should give some clue as to where the virus originated.
Investigators are also tracking the movement of people and supplies on the farm over the period that the infection is thought to have emerged.
The Department for Environment, Food and Rural Affairs (Defra) has asked farmers to monitor their flocks and report any symptoms immediately.
Defra officials are hoping that this is a one-off infection and can be quickly stamped out.
But it is likely the incident will be the first of many outbreaks in the coming months and years.
The United Nations' Coordinator for Bird Flu, David Nabarro, said that farmers would have to get used to the presence of the disease in the UK.
The risk to human health is low
"This virus is going to be in bird populations for several years to come. The way in which we'll deal with it is by implementing the well-rehearsed plan, which is to stamp it out at source.
"We've got to learn to accept that, not see it as a serious problem and just get on with normal poultry-rearing and consumption in the way that we tend to enjoy, and just see this as just one of those things that has to be dealt with through normal process."
The risk to human health is low. To date more than 150 people have died of the bird flu virus worldwide.
They are thought to have become infected through very close and prolonged contact with poultry. In the five outbreaks that have occurred in Europe, there have been no cases of human infection.
The Food Standards Agency has said that poultry and eggs are safe to eat if properly cooked.