The time-series model is based on the past epidemic situation of a disease to predict the future. This study predicted the incidence of HFMD in Beijing in 2020 without COVID-19 and NPIs, all of which fell within the 95% confidence interval, indicating a good fit and high prediction accuracy. However, in January 2020, the COVID-19 epidemic occurred in Beijing and a series of NPIs were implemented[11], resulting in an extremely low number of HFMD cases by 2020, with only 9.3% of the predicted number of cases throughout the year.
In 2020, COVID-19 broke out nationwide, and different cities faced various prevention and control problems and difficulties. In the early stages of an epidemic that lacks targeted preventive vaccines and drugs, NPIs are mainly used throughout the country to suppress the spread of the epidemic[12]; specifically, they include traditional infectious disease prevention and control measures, such as controlling the source of infection and cutting off the transmission routes. The implementation of these measures also affects the incidence rate of other infectious diseases. In 2020, COVID-19 in Beijing experienced three distinct stages: a domestic epidemic stage, in which cases were mainly imported from Wuhan; outbound import epidemic stage; and a local outbreak stage[13]. In the first half of 2020, offline teaching was suspended in Beijing, and primary and secondary schools and kindergartens opened successively in September[14]. Immediately thereafter, it ushered in only a small peak in HFMD incidence throughout the year. In a study by Geng[15], the national epidemic of HFMD was interrupted between February and August 2020 and rebounded after schools and kindergartens reopened in September, which is consistent with the results of this study.
HFMD and COVID-19 can be transmitted through close contact, respiratory tract, and other means. During epidemic prevention, China focused on strengthening intervention measures such as wearing masks, washing hands frequently, more ventilation, and less gathering, among others, while gradually cultivating good hygiene practices to inhibit the spread of HFMD. In June 2020, Beijing entered the stage of local cluster epidemic prevention and control, focusing mainly on the Beijing Xinfadi Market [13]. In previous years, June was the peak season for HFMD outbreaks in Beijing. At this time, due to the cluster epidemic in the local area, an emergency response to major public health emergencies was initiated, and prevention and control measures were tightened. Measures such as school and park closures, closed public places, and travel restrictions were implemented which greatly reduced opportunities for everyone to have contact and reduced the incidence of HFMD, while also avoiding the occurrence of clustered outbreaks of HFMD in schools and communities. The NPIs used to prevent COVID-19 can also significantly reduce the incidence of HFMD. In the future, good personal hygiene practices should be advocated in schools, kindergartens, and other key units.
This study had some limitations. Because HFMD is a self-limiting disease, patients are concerned about travel and medical treatment during the COVID-19 pandemic, causing fewer HFMD cases to be discovered, may resulting in a lower reported number than the actual number of infections.