INFECTIONS such as cold and flu may be a trigger for childhood cancers, North-East scientists revealed last night.

Researchers have examined hundreds of cases of childhood cancers going back 45 years.

The team was led by Dr Richard McNally, from the School of Clinical Medical Sciences, at Newcastle University, while statistics for the research were taken from the Manchester Children's Tumour Register.

Dr McNally intends to carry out a similar analysis of information held by the North of England Children's Cancer Register, in Newcastle.

It is thought that a virus can only affect babies and young children who have a genetic disposition towards childhood cancer.

However, the researchers stressed last night that people cannot "catch" cancer because an infection is likely to lead to the illness only in a very small number of children who are already susceptible to the disease.

They also discovered a pattern of cases where two types of cancer - leukaemia and brain tumours - repeatedly occurred at similar times and places, lending weight to fears of cancer clusters.

This so-called "space-time clustering" of cases is a pattern typical of diseases caused by infection, adding weight to the theory that outbreaks of infectious viruses are a potential contributory cause of cancer.

Diseases caused by environmental factors produce clusters of cases in one place over a much longer period of time.

The researchers carried out a sophisticated form of statistical analysis for the study, which is the first of its kind.

They looked to see if there was a pattern of certain types of cancers in relation to the time and place of children's births, and the time and place of where children were living when diagnosed.

Most significant were the clusters of leukaemia and central nervous system tumours found around the time and place of birth. In these, there were eight per cent more cases than could be explained by chance.

Clusters of acute lymphoblastic leukaemia and the brain tumour astrocytoma were also found around time and place of birth. Here there were 13 per cent more cases than expected.

There are theories that suggest environmental influences, such as viral infections, are part of the cause of cancer, in addition to genetic susceptibility. This research provides further evidence that this may be the case.