Scabies is a highly contagious parasitic skin disease caused by infestation with the Sarcoptes scabiei mite and affects an estimated 400 million people worldwide each year. Despite this substantial global burden and a rising incidence across Europe, fundamental epidemiological characteristics of scabies transmission have remained poorly defined. New research now provides important insights into the timing, growth, and control of scabies outbreaks.
Researchers analysed symptom onset data from four documented scabies outbreaks to estimate the serial interval, defined as the time between symptom onset in an index case and a secondary case. Serial interval estimates ranged from 98 to 167 days, with a pooled estimate of 123 days. This prolonged interval reflects the delayed symptom recognition and diagnosis commonly seen in scabies, which poses challenges for timely outbreak detection and containment in both community and institutional settings.
Scabies Reproduction Number Demonstrates Low but Sustained Growth
To assess broader transmission dynamics, the investigators examined national surveillance data from the Netherlands spanning 2011 to 2023. The analysis showed a steady increase in scabies-related healthcare consultations over time, with an estimated annual growth rate of 0.25 cases per 1,000 people. Using these data, the basic reproduction number (R₀) was estimated at 1.09, indicating low but sustained transmission sufficient to drive gradual epidemic growth.
Seasonal variation was also observed, with transmission peaking in July and consistent annual fluctuations in consultations. These findings suggest that environmental or behavioural factors may influence scabies spread and should be considered when planning public health interventions and dermatology service provision.
To support wider application of their analytical approach, the authors developed an open-source R package, {mitey}, which enables estimation of serial intervals and time-varying reproduction numbers. This tool may assist dermatology researchers and public health teams in analysing scabies outbreaks and evaluating control strategies.
Modelling results further indicated that preventing as little as 8% of secondary infections, through improved public awareness, early diagnosis, prompt treatment, and targeted contact management, could be sufficient to halt epidemic growth.
Clinical Implications of Scabies Epidemiological Modelling
The authors conclude that scabies transmission is characterised by long serial intervals and subtle but persistent growth, demonstrating the need for improved transmission data. For dermatologists, these findings highlight the importance of early recognition, timely treatment, and coordinated control measures to reduce the ongoing burden of this common skin disease.
Reference
Ainslie KEC et al. Estimation of the epidemiological characteristics of scabies. Nat Commun. 2025;16:10524.
