[Investigation on a seasonal influenza accompanying with the first locale novel A/H1N1 influenza outbreak in China].

Objective To timely summarize past experience and to provide more pertinent reference for control and prevention in A/H1N1 cases in influenza season. Methods During May 25 to 31,2009,2 secondary community cases caused by a influenza A/H1N1 imported case. In the close contacts of 3 A/ H1N1 cases, 14 had some aspiratory symptoms onset, such as fever(≥ 37.5℃), cough, sore throat and etc. Laboratory tests excluded the infection of A/H1N1 influenza. For throat swab test for the 14 cases,7 were tested for seasonal influenza virus. A face-to-face or telephone interview was conducted by CDC staff to collect information of 62 close contacts. Results Of 14 fever cases,there was no significant by differences by age [15-age group: 19. 2% (5/26), over 25-age group: 25.0% (9/36); χ2=0. 287, P=0. 592]; by sex group [24. 0% (6/25) for male and 21.6% (8/37) for female; χ2=0. 048, P=0. 826], by working units [dressing and design, photograph, saleroom and others, consumer group: 42. 1% (8/19), 27. 3% (3/11), 12. 5% (2/16) and 6. 3% (1/16); χ2=7. 653, P=0. 054], by dormitory style [dormitory style=33.3% (4/12),non-dormitory style=29.4%(10/34); χ2=0. 699,P=0. 403]. All the cases had fever (37.5-37.9℃),no case had diarrhea. One in 3 A/H1N1 cases had diarrhea. All the 14 cases were negative result for A/H1N1 RNA. Six from 7 cases were positive for seasonal influenza test. Conclusion This was a seasonal influenza outbreak happened in the close contacts of first confirmed A/H1N1 cases in community in mainland China. It showed that we should exclude the seasonal influenza in the investigation of A/H1N1 cases in the seasonal influenza period in some time. It is necessary to take effective measure to strengthen the control and prevention of seasonal influenza. Key words: A virus; H1N1 subtype;  Influenza; human;  Disease outbreaks;  Universal precautions