October 1942: a strange epidemic paralysis in Saval, Verona, Italy. Revision and diagnosis 50 years later of tri-ortho-cresyl phosphate poisoning.

In the autumn of 1942 a strange epidemic paralysis started in Saval, at that time a country area but now part of the city of Verona. The epidemic went on for several months and affected 41 people, all working as owners or labourers on the same farm. Some of the farm animals (chickens, horses, cattle, pigs) also became ill. About 20 patients were admitted to the nearby city hospital. The outbreak was diagnosed as polyneuritis with a probable viral cause. Fifty years later, seven people with sequelae of the disease were examined. The most severe cases present a spastic paraplegia and lower leg muscle atrophy without sensory impairment, resembling an amyotrophic lateral sclerosis "frozen" for 50 years. The clinical syndrome can now be attributed confidently to organophosphate induced delayed polyneuropathy. All the epidemiological data obtained from the survivors were evaluated and a careful review of the literature was made. Contamination of the ground from a rubbish dump near the farmyard would explain the epidemiology of the Saval outbreak.