To the Editor—Beginning in December 2019, a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused respiratory illness in infected persons, and the resultant disease was termed coronavirus disease 2019 (COVID-19). ^{Reference Heymann and Shindo1} By February 15, 2020, COVID-19 had rapidly spread throughout China and across the world, leading to a pandemic announced by the World Health Organization (WHO) on March 11, 2020. ^{Reference Ng, Marimuthu and Chia2} According to the WHO, as of November 14, 2020, there have been 53,164,803 confirmed cases of COVID-19, resulting in 1,300,576 COVID-19–related deaths. ³

With >50 million confirmed COVID-19 cases worldwide, China’s contribution of <100,000 cases, which were mainly identified in Wuhan province, seems low considering the country’s large population size. ⁴ With a series of effective interventions implemented in China, the spread of the virus was constrained within a short period. ^{Reference Wilder-Smith and Freedman5} Interestingly, these interventions also effectively blocked the transmission of other infectious diseases, such as influenza, tuberculosis, mumps, rubella, measles, and hand-foot-and-mouth disease (HFMD). ⁶ According to the Chinese Center for Disease Control and Prevention, both the peak incidences and the numbers of cases of measles, rubella, mumps, and HFMD were significantly lower in 2020 compared with those in 2019. Also, compared with those in 2019, the incidences of influenza and tuberculosis in 2020 were lower. However, the incidence of HFMD increased after September 2020. The incidences of these 6 diseases in 2019 and 2020 in China are shown in Figure 1.

Fig. 1. (A) The number of influenza cases in 2019 and 2020 in China. (B) Tuberculosis cases in 2019 and 2020 in China. (C) Rubella cases in 2019 and 2020 in China. (D) Measles cases in 2019 and 2020 in China. (E) Mumps cases in 2019 and 2020 in China. (F) Hand-foot-and-mouth disease (HFMD) cases in 2019 and 2020 in China.

Given that China’s response to COVID-19 did not include additional interventions against these infectious diseases, why the incidences of these diseases were also reduced during 2020 is an interesting question. The characteristics of the transmission of SARS-CoV-2 and the role of community in China’s response to COVID-19 are possible explanations. COVID-19 is an infectious respiratory disease transmitted mainly by respiratory droplets and close contact, and some studies have found that SARS-CoV-2 can be detected in fecal and urine samples of COVID-19 patients. ^{Reference Ong, Tan and Chia7} Because influenza, mumps, rubella, HFMD, and measles share similar routes of transmission, the following prevention and control measures against COVID-19 had played an important role in controlling their spread: (1) Local communities had strictly implemented the firmest regime of community isolation—large gatherings were prohibited; some companies and schools initiated “cloud working” and online courses, which helped maintain physical distancing. A physical distance of at least 1 m is probably associated with a large reduction in infection rates ^{Reference Chu, Akl and Duda8} ; thus, the COVID-19 preventive and control interventions could also effectively reduce the transmission of influenza, mumps, rubella, HFMD, and measles. (2) In response to the COVID-19 pandemic, China implemented a policy of maximized autonomous testing to enable more patients with respiratory infectious diseases, not just COVID-19, to receive timely testing and treatment, thus preventing the spread of other infectious diseases. ^{Reference Peto9} And (3) the government promoted simple but effective self-protection measures, such as mask wearing, hand washing and room ventilation. A preponderance of evidence has indicated that public mask wearing played the most effective role in stopping the spread of SARS-CoV-2. ^{Reference Chu, Akl and Duda8} The reason for the increase in the number of HFMD cases in October 2020 is not clear, but this may be related to the relaxed prevention and control measures in China.

Although the prevention and control measures against COVID-19 in some countries have improved, the risk posed by the pandemic will continue for a long time. Because these prevention and control measures can effectively prevent and constrain the spread of COVID-19 as well as other infectious diseases, and that the role of community isolation was fundamental among these measures, ^{Reference Li, Tan and Wu10} the implementation of these measures, especially community isolation, as normal prevention and control strategies and guidelines against COVID-19, seems to be a long-term process. However, whether these interventions will continue to be effective in preventing the spread of other infectious diseases in the long term or whether the incidences of other infectious diseases will rebound needs to be further studied.