Abstract
BACKGROUND: Measles, a highly contagious disease, still poses a huge burden worldwide. Lately, a trend of resurgence threatened the developed countries. A measles outbreak occurred in the Hong Kong International Airport (HKIA) between March and April 2019, which infected 29 airport staff. During the outbreak, multiple measures were taken including daily situation updates, setting up a public enquiry platform on March 23, and an emergent vaccination program targeting unprotected staff. The outbreak was put out promptly. The effectiveness of these measures was unclear. METHODS: We quantified the transmissibility of outbreak in HKIA by the effective reproduction number, R (eff)(t), and basic reproduction number, R (0)(t). The reproduction number was modelled as a function of its determinants that were statistically examined, including lags in hospitalization, situation update, and level of public awareness. Then, we considered a hypothetical no-measure scenario when improvements in reporting and public enquiry were absent and calculated the number of infected airport staff. RESULTS: Our estimated average R (0) is 10.09 (95% CI: 1.73-36.50). We found that R (0)(t) was positively associated with lags in hospitalization and situation update, while negatively associated with the level of public awareness. The average predicted basic reproduction number, r (0), was 14.67 (95% CI: 9.01-45.32) under the no-measure scenario, which increased the average R (0) by 77.57% (95% CI: 1.71-111.15). The total number of infected staff would be 179 (IQR: 90-339, 95% CI: 23-821), namely the measure induced 8.42-fold (95% CI: 0.21-42.21) reduction in the total number of infected staff. CONCLUSION: Timely reporting on outbreak situation and public awareness measured by the number of public enquiries helped to control the outbreak.