They use statistical models designed to calculate so-called excess mortality that occurs during the period when influenza viruses are circulating widely in a given population.
2
在19世纪开始采用估算超额死亡率的方法以便记录原本会被忽略的这些与流感相关的死亡。
Methods for estimating excess mortality were introduced in the 19th century to capture these influenza-associated deaths that would otherwise be missed.