Assessing the impact of respiratory infections and weather conditions on donor attendance and blood inventory in Hong Kong.

Background Maintaining a stable, safe and sufficient blood supply is crucial to the healthcare system. Every year, seasonal influenza epidemics lead to substantial hospitalizations and pose intense pressure on blood transfusion service worldwide, especially in an ageing population of Hong Kong which often see bi-annual influenza outbreaks. However, limited quantitative studies have been performed to assess the impacts of influenza and other respiratory infections on blood supply. Methods We estimated the impacts of respiratory infections on donor attendance and blood inventory, considering the confounding effects of weather conditions. The method only required influenza-like illness data from the existing sentinel surveillance network, local weather data, donor attendance records from blood transfusion service and blood inventory levels from local healthcare system. Results We estimated the number of donor attendance dropped by 6-10% when the number of consultations with influenza-like illnesses (ILIs) reported by sentinel general outpatient clinics exceeded five per 1000 consultations, which is a moderate activity level and has been observed frequently in Hong Kong. Blood inventory decreased with increased ILI consultation rates reported by sentinel general outpatient clinics. Adverse weather conditions had negative impacts on both donor attendance and blood inventory. Conclusion Epidemics of influenza and other respiratory infections coupled with adverse weather conditions affected blood supply in Hong Kong. The pressure on blood transfusion service to maintain a stable and sufficient blood supply during influenza seasons should not be overlooked, especially in an ageing population of Hong Kong.