(WHO) issued a global alert describing cases of atypical pneumonia of unknown cause appearing in Hong Kong, China, and Vietnam. 1 As of April 28, 2003, severe acute respiratory syndrome (SARS) has been described in 28 countries involving 5050 individuals Early Release: This article as posted online at http:// www.jama.com on May 6, 2003. Author Affiliations are listed at the end of this article.

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To determine factors that predispose or protect healthcare workers from severe acute respiratory syndrome (SARS), we conducted a retrospective cohort study among 43 nurses who worked in two Toronto critical care units with SARS patients. Eight of 32 nurses who entered a SARS patient’s room were infected. The probability of SARS infection was 6% per shift worked. Assisting during intubation, suctioning before intubation, and manipulating the oxygen mask were high-risk activities. Consistently wearing a mask (either surgical or particulate respirator type N95) while caring for a SARS patient was protective for the nurses, and consistent use of the N95 mask was more protective than not wearing a mask. Risk was reduced by consistent use of a surgical mask, but not significantly. Risk was lower with consistent use of a N95 mask than with consistent use of a surgical mask. We conclude that activities related to intubation increase SARS risk and use of a mask (particularly a N95 mask) is protective.

Since 1967, 40 patients with hydatid disease of the liver have been treated at our hospital. Diagnosis was made using clinical criteria, serology, skin tests, and imaging techniques. Thirty-five patients were operated upon. In 18 patients the cyst was uncomplicated (Group I), and in 17 the cyst was infected or communicated with the biliary tract (Group II). Three forms of surgical treatment were used: A) cyst evacuation, scolicidal irrigation, and primary cyst closure, B) evacuation, irrigation, and external drainage, and C) complete or partial cyst resection. Mebendazole was used in six patients, four of whom were also treated surgically. In Group I, one of 11 patients (8%) treated by primary closure had complications, versus four of five patients (80%) treated with external drainage (p less than 0.001). Mean postoperative hospital stay for these two groups was 11.8 versus 20.8 days, respectively (p less than 0.001). Complication rates in Group II were higher, and were evenly distributed among treatments. Patients have been followed yearly, with a median follow-up of 5 years. Active hydatid disease has been found in three patients, who all had known residual disease at initial operation. The best treatment for an uncomplicated hydatid liver cyst is evacuation, scolicidal irrigation, and primary closure. External drainage is used for infected cysts or those communicating with the biliary tract, and excision for extrahepatic and peripheral, easily resectable cysts. Mebendazole is used for intraperitoneal spillage of cyst contents and in patients with inoperable disease.