[Pattern on the spread of novel influenza A (H1N1) and quantitative assessment of containment in mainland China]

Abstract

Objective: To study the epidemic tendency of emerging influenza A (H1N1) in mainland China, and to explore the different patterns of spread on the disease under the following contexts: (1) To stop the temperature screening program at the border areas of the country; (2) To stop measures of prevention and control on those identified cases and their close contacts; (3) To strengthen programs for the foreign immigrants on 'home quarantine'.

Methods: Under relevant parameters and information on the transmission link from different reference data, the patterns of influenza spread were simulated by Monte Carlo method.

Results: The temperature screening on border could inhibit the transmission of influenza A (H1N1) to some extent, so that after 3 months the cumulative number of cases will be reduced by 21.5% (1718 cases) and transmission speed of influenza A (H1N1) in mainland China will be delayed by about 4 days. Furthermore, taking positive measures of prevention and control could efficiently slow down the epidemic, so that after 3 months the cumulative number of cases will be reduced by 93.4% (about 90 thousand cases) and it would be delayed by about 15 days if influenza A (H1N1) spreads to the whole country. In addition, if the immigrants were able to practise quarantine measures consciously by themselves at home the effect of prevention and control against influenza A (H1N1) would be more significant. If 30%, 60% and 90% of immigrants would take quarantine measures home consciously, after 3 months the cumulative number of cases will be reduced by about 15% (about 940 cases), 34% (about 2230 cases) and 64% (about 4180 cases), respectively. Also, influenza A (H1N1) spreads to the whole country will be delayed by about 4 days, 10 days and 25 days, respectively. It is difficult to curb fully the development of the epidemic by taking existing control measures, and influenza A (H1N1) may spread to almost all provinces after about 3 months.

Conclusion: The effects of existing prevention and control measures were objectively assessed and the results showed the necessity and effectiveness of these measures against the transmission of influenza A (H1N1), in the mainland of China.