Massive scabies outbreak in Rohingya refugee camps, Cox’s Bazar: Epidemiology and impact of a mass drug administration (MDA) campaign – A retrospective study

BACKGROUND: Since 2021, Rohingya refugee camps in Cox's Bazar, Bangladesh, have experienced a significant and concerning increase in the prevalence of scabies. In response to the massive outbreak, an extensive Mass Drug Administration (MDA) campaign was conducted by WHO Bangladesh, in collaboration with the Government of Bangladesh and Health Sector partners, from November 29, 2023, to February 01, 2024. OBJECTIVES: The objectives of the study were: a) to determine the epidemiological characteristics (i.e., magnitude, age-sex distribution, and attack rate) of the scabies outbreak in the Rohingya refugee camps; and b) to evaluate the impact and durability of MDA in reducing the burden of scabies in the refugee camps. METHODOLOGY: This was a retrospective observational study that utilized deidentified and anonymized data from 35 health facilities of the International Organization for Migration (IOM) spanning the period from January 1, 2021, to December 31, 2024. RESULTS: A total of 384,852 cases of scabies were reported, with an overall attack rate of 5,562.59 scabies cases per 10,000 population over 4 years. Females had a slightly higher case proportion (53.51%) and attack rate (ARR: 1.104, p < 0.001). Children under 5 years (36.31%) had the highest burden and attack rate, about twice the overall attack rate. Using this age group as reference, the attack rate declined significantly with increasing age, 5,561.85 among adolescents (ARR: 0.496, p < 0.001) to 4,377.88 among individuals over 60 years (ARR: 0.390, p < 0.001). 77% of the cases were reported among the Rohingya refugees; however, the attack rate was higher among host communities (7,721.34 per 10,000 vs. 5,138.24 per 10,000 among refugees). Overall, 5.80% of scabies cases were associated with secondary bacterial infections. Interrupted time series (ITS) analysis showed a sharp and immediate decline in scabies cases following MDA initiation, representing a reduction of 1,885 cases per week (p < 0.001) - equivalent to a weekly decline of approximately 100% from the pre-MDA peak. The decline persisted for 6 months (decreasing trend of 69.98 cases/week, p < 0.001), after which a statistically significant upward rebound was observed (72.04 additional cases per week, p = 0.002). CONCLUSION: The study revealed a high burden of scabies among the Rohingya refugees and the adjacent host community. MDA was an effective approach for a rapid and substantial reduction of the disease burden. However, the impact cannot be sustained unless the underlying factors of the scabies outbreak are addressed.