In fact she was displaying the potentially fatal symptoms of Toxic Shock Syndrome and Necrotising Fasciitis, also known as the flesh-eating bug, which are rare but known complications of chicken pox.

Ordeal

She was transferred to hospital with multiple organ failure in April 1999 and spent four weeks in intensive care.

Isabel, now six, survived the ordeal but will need further operations.

Her parents Jason and Charlotte Maude decided not to sue the NHS over her treatment.

Instead they worked with the paediatric consultant at St Mary's Hospital in Paddington, who helped save Isabel's life, to develop the online diagnosis system.

Blame

Developed by The Isabel Medical Charity, it uses pattern recognition software to search for information in paediatric textbooks.

By typing in initial patient symptoms, clinicians can see a set of possible diagnoses within seconds.

Isabel's mother, Charlotte, said to blame doctors for what had happened to her daughter would have "achieved nothing", but "if Isabel saves just one child's life, it has all been worthwhile".

She and her husband, who quit his job to help develop Isabel and raise funds for the charity, are now hoping there will soon be an adult version of the system.