Letter: Cancer viruses

Sir: Two years ago, the son of my friend Mary Hurst was diagnosed with acute myeloid leukaemia. Not content with being told that the cause was unknown, Mrs Hurst embarked on investigations which led us both to study the literature on the subject.

We came to the same conclusion as Professor Kinlen and Sir Richard Doll - that leukaemia is caused by a virus ("Found: the cause of leukaemia", 14 August). There is an established mechanism for this. For example, the SV40 virus is capable of translocating chromosomes, alerting the growth cycle of cells, and disabling the killer cells which would normally destroy cancer cells.

However, if Professor Kinlen's idea that clusters of childhood leukaemia are caused by viruses introduced into a local community by the movement of migrant workers is correct, then bearing in mind the massive increase in transmigration of peoples over the last 30 years, one would expect the incidence of leukaemia to reach epidemic proportions. This would not seem to be case.

The SV40 virus is present in about 5 per cent of people. In the vast majority, it does not appear to cause any harm. However if a person's immunity is compromised, for whatever reason, then this may be all that is required for the leukaemia to be triggered in a susceptible person.

We feel it is vital that when a person presents with leukaemia, their blood cells are checked for SV40 and other viruses, prior to the commencement of chemotherapy.

If this hypothesis is correct, then perhaps one day a vaccine will be produced.

Dr ANDREW NORMAN

Poole, Dorset