Risk index and early-warning model of H7N9 human infections / 预防医学

ABSTRACT

Objective To establish the risk index of early-warning on the human infections with avian influenza A (H7N9) virus. Methods The risk index (X) was calculated by using Principal Component Analysis based on the surveillance results (including the positive rates of environmental specimens and premises) during the period from April 2013 to March 2017 in Zhejiang Province. Then, the method of Classification and Regression Trees was used to establish the early-warning model for forewarning the epidemic situation of H7N9 human infections. Results The weights of two rates (the positive rates of specimens and premises) used to establish the risk index were 0.0545 and 0.0230 respectively. In the model of Classification and Regression Trees, risk index was divided into 4 grades X ≤0.140, 0.140<X ≤0.757, 0.757<X ≤3.285 and X>3.285. Compared to the 1st grade, the risk ratios of the 2nd, 3rd and 4th grades were 7.4, 21.7 and 29.9 respectively. The accuracy, sensitivity and specificity of prediction were 86.1％ , 80.8％ and 87.3％ respectively, and the Kappa value was 0.592 . Conclusion The established risk index can be used to forewarn the H7N9 human infections, which is helpful for emergency preparedness and disease control.