According to the demographic information of SARS patients, infection occurred in all age groups (the average age was ≦45) [37]. There was a proportional difference between male and female (female predominance) [37], with a male-to-female ratio of 1:1.25 [38]. In addition, hospital staff had a higher risk due to the proximal interactions with large numbers from the infected population. For example, hospital staff accounted for 22% of all cases in Hong Kong and 22.8% in Guangdong [37]. The mortality caused by SARS increased with age (> 64 years) [37], and the overall mortality rate during the outbreak of SARS was estimated at 9.6% [39,40].