Moving-average based index to timely evaluate the current epidemic situation after COVID-19 outbreak

A pneumonia outbreak caused by a novel coronavirus (COVID-19) occurred in Wuhan, China at the end of 2019 and then spread rapidly to the whole country. A total of 81,021 laboratory-confirmed cases, including 3,194 deaths (3.9%) had been reported in China by March 14, 2020, meanwhile, 61,518 laboratory-confirmed cases and 2,199 deaths were reported outside China. Common symptoms of COVID-19 pneumonia included fever, fatigue and dry cough. Faced with such a sudden outbreak of new infectious diseases, we have no history to learn from and no evidence to count on. Traditional models often predict inconsistent results. Aiming at estimate the epidemic trend timely after the outbreak, we mainly used 7-day moving average of log-transformed daily new cases (LMA) to establish a new index named "epidemic trend index", which will be used to predict the evolutionary trend of the epidemic situation and support epidemic control decision making processes. We used SARS epidemic data from Hong Kong in 2003 to verify the practicability of the new index, which shows that the index is acceptable. The epidemic trend index was then applied to the COVID-19 epidemic analysis in China. The results show that during the epidemic, the trend direction of different districts of China changed on different date. In the whole country and in Hubei Province alone, the epidemic reached the peak on February 9. While the peak appeared earlier, i.e. on February 5 in other provinces. It indicated that decisive outbreak control measures of the Chinese government are effective. While local governments should adjust management measures based on local risk level of epidemic. Although the epidemic has eased since late February, continued efforts in epidemic control are still needed to accelerate the end of the epidemic in China. However, the global COVID-19 epidemic outside China continues to expand as indicated by the epidemic trend index we proposed. In order to cope with the novel coronavirus pandemic, people all over the world should work together and governments of all countries should take efficient measures in the light of China's experience and according to national circumstances and local conditions.