Abstract: Based on the daily meteorological data and influenza A (H1N1) case data of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), a climate suitability model was used to calculate, evaluate, and predict the climate suitability and its spatiotemporal differences for the transmission of H1N1 in GBA during winter. The results showed that the climate suitability index for H1N1 transmission was relatively high from late December to next mid-February, with a small coefficient of variation. The suitability index peaked in late January, indicating the most suitable period for H1N1 transmission. Over the past 42 years, the climate suitability index for H1N1 transmission in GBA during winter showed a downward trend, with a significant decrease after 2015. From a monthly perspective, the climate suitability index in December and January showed a consistent increasing trend, but a significant decreasing trend in February. Moreover, the climate suitability for H1N1 transmission showed a spatial pattern of decreasing from northwest to southeast, with the suitability index in the northwest region being 1.5 to 2 times that in the southeastern coastal areas. In terms of variation trends, the suitability for H1N1 transmission was increasing in the eastern area of west side of the Pearl River Estuary and some regions of Huizhou, particularly in Foshan and Zhongshan, with an increase rate exceeding 1.0(10 a)^-1, while the coastal areas showed a downward trend, with a reduction rate of more than 0.05(10 a)^-1. In conclusion, the critical period for the H1N1 transmission was from the Winter Solstice to the Beginning of Spring of the following year, and the key areas of focus were the core cities of the west of the Pearl River Estuary.

Key words: climate suitability index, influenza A (H1N1), climate change, Guangdong-Hong Kong-Macao Greater Bay Area