Seasonality of scabies and its association with climatic factors in Rohingya refugee camps, Cox's Bazar: a retrospective observational study, 2021-2023.

backgroundScabies is a common skin condition and poses a substantial disease burden in resource-poor tropical settings. The Rohingya refugee camps in Cox's Bazar, Bangladesh represent one of the world's largest and most protracted humanitarian crises. Using 3 years of data from 2021 to 2023, this study analysed the seasonality of scabies and examined its association with climatic factors.

methodsThis is a retrospective observational study conducted in the Rohingya refugee camps and adjacent host communities in Ukhiya and Teknaf, Cox's Bazar. All patients clinically diagnosed with scabies and who received treatment at 35 International Organization for Migration (IOM)-supported health facilities between 1 January 2021 and 31 December 2023 were included. Climate data, including daily mean, minimum and maximum temperature and total and maximum rainfall, were obtained from the Bangladesh Meteorological Department. Seasonal-Trend decomposition using LOESS (locally estimated scatterplot smoothing) (STL) was applied. Associations between climatic variables and the decomposed seasonal component of scabies cases and corresponding attack rate, as well as overall scabies case counts and overall attack rate, were assessed using Pearson's correlation tests.

resultsA total of 323 106 new scabies cases were reported from IOM-supported health facilities between January 2021 and December 2023. Children aged under 5 years and 6-18 years accounted for the highest proportion of cases (32.08% and 38.95%, respectively). The average monthly number of scabies cases was highest in November (12 625) and lowest in May (5862). Case numbers increased from November to February (high season), with a peak between October and November, and declined between April and June (low season). An inverse relationship was observed between temperature and scabies incidence, with higher case numbers during cooler months and lower numbers during warmer months. Pearson's correlation analysis demonstrated a strong and significant negative correlation between the seasonal components of both scabies cases and attack rate and temperature variables, including maximum (cases: r=-0.492, p=0.002; attack rate: r=-0.484, p=0.003), minimum (cases: r=-0.506, p=0.002; attack rate: r=-0.489, p=0.002) and mean temperature (cases: r=-0.525, p=0.001; attack rate: r=-0.511, p=0.001). No significant association was observed between the seasonal component of scabies cases or attack rate and humidity or rainfall.

conclusionThis study identified a distinct seasonal pattern of scabies, with higher caseloads and attack rate during late autumn and winter (October to February) and lower caseloads and attack rate during summer months (April to June). Temperature showed a strong negative association with the seasonal component of scabies burden. These findings may inform the timing of public health strategies, including mass drug administration, intensified case management and social and behavioural change communication, in humanitarian settings.