Objectives: To evaluate the impact of a severe acute respiratory syndrome (SARS) outbreak in the emergency department (ED).

Methods: Computerised records of all ED visits in January and May 2003 were analysed and compared, representing before and during the SARS epidemic respectively. Data were grouped into two categories. Group 1 was the indicators of impact on patients, including visitor's condition classification, number of patients that died on arrival (DOA), received cardiopulmonary resuscitation, underwent endotracheal intubation, needed mechanical ventilation, discharged against medical advice (AAD), died in the ED, and the admission rate to wards. Group 2 was the indicators of impact on the quality of medical care, including number of visits that returned within 72 hours (early returns), underwent chest radiography, upper abdomen sonography or computed tomography, and the length of stay.

Results: There were 6650 and 3901 consecutive encounters in January and May 2003 respectively. There were significant differences on condition classifications (p = 0.000), increased rate of patients that underwent endotracheal intubation (p = 0.003), needed mechanical ventilation (p = 0.020), and admission (p = 0.000). The rate of AAD decreased significantly (p = 0.024). There was no significant difference on early returns, although the length of stay in the ED increased (p = 0.043). The number of visits that underwent chest radiological examination increased (p = 0.000) and upper abdomen sonography (p = 0.007) decreased significantly in May.

Conclusions: SARS had an impact on the medical service system and decreased visits by 40% in the ED. Patients visiting the ED had more severe conditions than before. The impact of SARS on quality of medical care can be minimised when adequate infection control measures are applied.