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Background: Dengue fever is an infectious disease of global health concern. This study aimed to describe the epidemiology and field experience of a locally transmitted outbreak of dengue fever in Muscat Governorate, Oman from mid-March to mid-April 2022, and the multi-sectoral approach to control the outbreak. Methods: Data were collected from an electronic e-notification system, active surveillance and contact investigations. Results: Of 250 suspected and probable cases, 169 were confirmed as dengue fever with DENV-2 serotype. Of these, 108 (63.9%) were male and 94 (55.6%) were Omani. The mean age was 39 years (standard deviation 13 years). Fever was the most common symptom and occurred in 100% of cases. Haemorrhagic manifestations occurred in 10% (n=17) of cases. Hospitalization was required for 93 cases (55.1%). The field investigation included 3444 houses and other suspected sites. Breeding sites for Aedes aegypti were identified in 565 (18.5%) sites visited. Interventions to control the outbreak included environmental and entomological assessment of the affected houses and surrounding areas (400 m radius of each house). Conclusion: Outbreaks are expected to continue, with the possibility of severe cases due to antibody-dependent enhancement. More data are required to understand the genetics, geographical spread and behaviour of A. aegypti in Oman.

Highlights • Rt can be used to closely monitor the non-pharmaceutical interventions (NPI) of COVID-19 epidemic. • Generally, the activity of the epidemic in Oman. • Other factors, like the return of overseas students, have increased the epidemic activity. • Responses to NPI is different between migrants and natives., Background COVID-19’s emergence carries with it many uncertainties and challenges, one of which is epidemic management strategies. Oman has implemented non-pharmaceutical interventions (NPIs) to mitigate the impact of COVID-19. However, responses to NPIs may be different across different populations in a country with a large number of migrants like Oman. This study investigates the different responses to NPIs assessing the use of time-varying reproduction number (Rt) to monitor it. Methods Polymerase chain reaction (PCR) laboratory-confirmed COVID-19 data from Oman was used from February 24th to June 3rd, 2020 and included demographic and epidemiological information. Data were arranged into pairs of infector–infectee, and two main libraries of R software were used to estimate reproductive number (Rt). Rt was calculated for both Omanis and non-Omanis. Findings A total of 13,538 cases were included, 44·9% of which were Omanis. Among all, we identified 2769 infector–infectee pairs to calculate Rt. There was a sharp drop in Rt from 3·7, (95% confidence interval [CI] 2·8-4·6) mid-March to 1·4 (95% CI 1·2–1·7) in late March in response to NPIs. Then Rt decreased to 1·2 (95% CI 1·1–1·3) late April when it rose, corresponding to the easing up of NPIs. Comparing the two groups, the response to major public health controls was more evident in Omanis in reducing the Rt to 1·09 (95% CI 0·84–1·3) at the end of March. Interpretation Use of real-time estimation of Rt has allowed us to follow the effect of NPIs. The migrant population responds differently than the Omani population.