Objective To investigate and manage an imported dengue fever (DF) outbreak in Shanghai in 2024, to summarize the experience and lessons learned from the on-site management, and to provide a reference basis for future prevention and control of DF.

Methods Epidemiological investigation and case search were carried out for an imported DF outbreak in Shanghai, 2024. Real-time fluorescence polymerase chain reaction (RT-PCR) was used to detect dengue virus nucleic acid in the serum samples from cases. Meanwhile, emergency vector surveillance and mosquito control measures were carried out in the affected areas, and the effectiveness of the management was evaluated.

Results According to the epidemiological investigation, it was confirmed that this epidemic was a family cluster of imported DF, with both cases infected in Thailand and developed symptoms successively after returning to Shanghai. Laboratory testing identified the pathogens as dengue virus serotype-3 (DENV-3). In the core and precautionary area, ultra-low-volume space spraying and residual spraying were combined to kill adult mosquitoes, and at the same time, comprehensive cleaning and elimination of mosquito breeding sites was carried out. After 2 weeks, the Breteau Index (BI) in the core area decreased from 20 to 5, and the mosquito net trap index decreased from 2 mosquitoes (net·hour)^-1 to 0.67 mosquitoes (net·hour)^-1. Continuous implementation of mosquito control measures kept the BI and net trap index below the safety thresholds BI<5 and mosquito net trap index <2 mosquitoes (net·hour)^-1 both in the core and precautionary area.

Conclusion Early diagnosis and isolation of patients, combined with rapid suppression of the density of vector Aedes mosquitoes, are the key measures to prevent the transmission of imported DF cases.