The relative index of potential contamination(IPC)was 67.2% in the age group 20-49 years,this group was considered as the main transmission source in the population.

• 各年龄组污染指数（IPC）以30－39岁年龄组最高（79.；1），相对IPC也以30－39岁年龄组最高，20－49岁相对IPC为67