Viper bites: treat or ignore? Review of a series of 99 patients bitten by Vipera aspis in an alpine Swiss area.

In a well defined alpine area of Switzerland (Valais, about 300000 inhabitants, tourists included) we studied retrospectively over 32 years, 99 patients bitten by vipers (Vipera aspis, the likely unique species in this area). The annual incidence was estimated at 3/100,000, as in other European countries. The mortality was 0% for the adults. The patients, 72 adults and 17 children (13 years and less), were classified in four groups: grade 0 no envenomation (8%), grade 1 minimal (42%), grade 2 moderate (40%), and grade 3 severe envenomation (10%). The 10 patients of grade 3 showed impressive clinical signs and blood abnormalities, as exemplified by our three most severe cases. Only patients of grade 3 must be treated with antivenom and other intensive treatments, but all patients, even grade 1, especially small children, must be observed for several hours.