Intensity and Drivers of Subtypes Interference Between Seasonal Influenza Viruses in Mainland China: A Modelling Study

Subtypes interference has a significant impact on the epidemiological patterns of seasonal influenza viruses (SIVs). We used attributable risk percent [the absolute value of ratio of the effective reproduction number (Rₑ) of different subtypes minus one] to quantify interference intensity between A/H1N1 and A/H3N2, as well as B/Victoria and B/Yamagata. The interference intensity between A/H1N1 and A/H3N2 was higher in southern China 0.26 (IQR: 0.11 - 0.46) than in northern China 0.17 (IQR: 0.07 - 0.24). Similarly, interference intensity between B/Victoria and B/Yamagata was also higher in southern China 0.14 (IQR: 0.07 - 0.24) than in norther China 0.10 (IQR: 0.04 - 0.18). High relative humidity significantly increased subtypes interference, with the highest relative risk reaching 20.59 (95% CI: 6.12 - 69.33) in southern China. Southern China exhibited higher levels of subtypes interference, particularly between A/H1N1 and A/H3N2. Higher relative humidity has a more pronounced promoting effect on subtypes interference.