UC Irvine

Abstract: Background. Future distribution of dengue risk is usually predicted based on predicted climate changes using general circulation models (GCMs). However, it is hard to validate the GCM results and assess the uncertainty of the predictions. Observed changes in climate may be very different from GCM results. Methods.We collected Aedes albopictus surveillance data and observed climate records from about 90 meteorological stations for the period 1970–2021. We analyzed the trends of climate change in China and made predictions on future climate for the years 2050 and 2080 based on trend analyses. We analyzed the relationship between climatic variables and the prevalence of Ae. albopictusin different months/seasons. We built a series of machine learning classification tree models to predict the monthly/seasonal Ae. albopictus distribution based on the average climate from 1970 to 2000 and assessed the contributions of different climatic variables to the Ae. albopictus distribution. Using these models, we projected the future distributions of Ae. albopictus for the years of 2050 and 2080. Results. The study included Ae. albopictus surveillance from 259 sites in China and found that winter to early spring (November–February) temperatures were strongly correlated with Ae. albopictus prevalence – the higher the temperature the higher the prevalence, while precipitation in summer (June–September) was important predictors for Ae. albopictus prevalence. The machine learning tree models predicted the current prevalence of Ae. albopictus with high agreement (accuracy > 90% and Kappa agreement > 80% for all months). Overall, winter temperature contributed the most to Ae. albopictus distribution, followed by summer precipitation. Increase in temperature was observed in most places in China and rates of annual change varied substantially among sites, with the highest increase in temperature occurring from February to April (annual increase of 1.4 – 4.7ºC for monthly mean, 0.6 – 4.0ºC for monthly minimum, and 1.3 – 4.3ºC for monthly maximum temperature) and the lowest in November and December. Temperature increases were lower in the tropics/subtropics compared to the high-latitude areas. The projected temperatures in 2050 and 2080 by this study were about 1~1.5°C higher than projected by GCMs. The estimated current Ae. albopictus risk distribution had a northern boundary of north-central China and the southern edge of northeastern China, with a risk period of June–September. The projected future Ae. albopictus risks in 2050 and 2080 cover nearly all of China, with an expanded risk period of April–October. The current at-risk population was estimated to be 960 million and the future at-risk population was projected to be 1.2 billion. Conclusions.The magnitude of climate change in China is likely to surpass the GCM predictions. Future dengue risks will expand to cover nearly all of China if the current climate trends continue.