RESUMEN
<p><b>OBJECTIVE</b>To analyse the severe acute respiratory syndrome (SARS) epidemics in Inner Mongolian Autonomous Region and to provide scientific basis for prevention and control strategies against it.</p><p><b>METHODS</b>Data from legal communicable diseases surveillance reporting system was analyzed epidemiologically.</p><p><b>RESULTS</b>The first SARS case was reported in Inner Mongolian Autonomous Region on March 27, 2003. Up to May 20, there were 446 cumulative SARS cases in the whole region (with 287 confirmed cases and 159 suspected cases) and 61 cumulative recovered cases had been discharged from the hospitals (56 confirmed cases and 5 suspected cases). Another 131 cases were excluded the original diagnoses of SARS including 10 confirmed cases and 121 suspected cases. 25 confirmed cases died with a mortality rate of 8.7%. Cumulatively, the number of reported cases were distributed in 30 counties in 9 prefectures. Statistical analysis on time sequence of the occurrence of cases showed that majority (67.7% of the total) of the cases concentrated in between April 13 and April 29. The number of cases had started to decrease since April 24 with an average of 5.3 cases per day between May 3 and May 8 and an average of 0.3 cases per day between May 9 and today.</p><p><b>CONCLUSIONS</b>SARS epidemics in our region could be divided into three phases. The first phase fell in between March 18 and April 15 with the first case being imported, the number of cases rose sharply, covering 14 counties in 6 prefectures, having a feature of family clustering. The second phase was from April 16 to April 28, with the appearance of secondary infection, having sharp rise of the cases and spreading to 24 counties in 10 prefectures. One of the major features was that hospitals had become the important sources of secondary infection. Finally, the third phase was between April 29 and May 20, with small wave crests of cases, spreading to 38 counties in 10 prefectures with a high proportion of cases with no history of direct contact with diagnosed SARS patients. Thus, no obvious transmission chain was noticed at this phase.</p>