Approaches to co-occurrence: Scurvy and rickets in infants and young children of 16–18th century Douai, France

Disease co-occurrence is defined as the presence and interaction of multiple diseases in a single individual. The phenomenon occurred in the past, but detailed analyses of individuals affected by co-occurrence seldom appear. This paper presents 12 possible cases of scurvy and rickets co-occurrence from the Saint-Amé skeletal collection in Douai, France, dated to the 16-18th century. Each individual was evaluated for evidence of both diseases using macroscopic and radiographic techniques. Additional backscatter scanning electron microscopy evaluation for evidence of rickets was completed on a sub-sample of seven co-occurrence cases. Co-occurrence detection increased with the use of multiple techniques. No unique features identifying scurvy and rickets co-occurrence were observed; instead features associated with both diseases were present. Following clinical expectations, scurvy features were clearly developed while rickets features were subtle. Possible disease sequence and socio-cultural implications are suggested. The study's findings are important to further research on disease co-occurrence as information on cases enhances our ability to understand site context.