Epidemiologic clues to SARS origin in China

Abstract

An epidemic of severe acute respiratory syndrome (SARS) began in Foshan municipality, Guangdong Province, China, in November 2002. We studied SARS case reports through April 30, 2003, including data from case investigations and a case series analysis of index cases. A total of 1,454 clinically confirmed cases (and 55 deaths) occurred; the epidemic peak was in the first week of February 2003. Healthcare workers accounted for 24% of cases. Clinical signs and symptoms differed between children (<18 years) and older persons (> or =65 years). Several observations support the hypothesis of a wild animal origin for SARS. Cases apparently occurred independently in at least five different municipalities; early case-patients were more likely than later patients to report living near a produce market (odds ratio undefined; lower 95% confidence interval 2.39) but not near a farm; and 9 (39%) of 23 early patients, including 6 who lived or worked in Foshan, were food handlers with probable animal contact.

Figure 1

Epidemic curve of cases of severe acute respiratory syndrome by date of onset, November 1, 2002–April 30, 2003, in Guangdong Province, China, showing cases in the community and in healthcare workers.

Figure 2

Geographic distribution of population in: (A) urban districts of Guangzhou city, (B) Guangdong Province and district-specific incidence of severe acute respiratory syndrome (per 100,000 population).

Figure 3

Timeline of cases of severe acute respiratory syndrome by week of onset, November 1, 2002–April 30, 2003, in the seven predominantly affected municipalities of Guangdong Province, China.

Figure 4

Number of patients with severe acute respiratory syndrome by age, and age-specific incidence (per 10,000 population), November 1, 2002–April 30, 2003, Guangdong Province, China.

Figure A1

Timeline of cases of severe acute respiratory syndrome by date of onset and chains of transmission, November 16, 2002-February 10, 2003, Foshan municipality, Guangdong Province, China. A: Index patient and family cluster. B: Family and healthcare workers cluster. C: Healthcare worker cluster at township hospital. D: Workplace cluster. Case-patients 6, 10, 18, and 26 had no contact history. Dark box: food handler, light box: healthcare worker.