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, which suggested that non-pharmaceutical interventions (NPI) implemented during the COVID-19 pandemic influenced the incidence of other respiratory diseases transmitted through respiratory droplets and aerosols. There were also several other reports indicating that the COVID-19 pandemic affected the incidence of influenza and other human respiratory infections such as pertussis, scarlet fever and hand-foot-mouth disease.
However, there is a lack of data on seasonal trends of other common respiratory infections such as measles and mumps impacted by NPI strategy during the COVID-19 pandemic.
Measles is an acute respiratory infection whose basic reproduction number is currently the highest (R0 = 18).
It can occur round the year and is prevalent in the winter and spring. Although the above-mentioned infectious diseases can be prevented by vaccination, the World Health Organization (WHO) reported that the epidemiological trends of the infectious diseases have changed globally due to the impact of the COVID-19 pandemic.
MMWR Morb Mortal Wkly Rep.2021; 70 (Nov 12PubMed PMID:34758014. Pubmed Central PMCID: PMC8580203 Journal Editors form for disclosure of potential conflicts of interest. Matt Ferrari reports grants from the Bill and Melinda Gates Foundation, the World Health Organization (WHO), and Gavi, the Vaccine Alliance, to develop measles models and travel support from WHO to attend the Strategic Advisory Group of Experts on Vaccines (SAGE) meeting in 2019 and the Measles and Rubella SAGE working group. Allison Portnoy reports grant support from The Pennsylvania State University for time and analytic contributions to this manuscript. No other potential conflicts of interest were disclosed. Epub 2021/11/11. eng): 1563-1569
Considering the public health risks posed by these infectious diseases and taking into account the COVID-19 prevention and control strategies in mainland China, we conducted a comparative analysis to explore the impact of COVID-19 pandemic on measles and mumps infections in mainland China. It will facilitate the design of more effective key interventions and preventive measures to combat these resurgent infectious diseases.
Surveillance data for infectious diseases collected from January 2017 to August 2022 were extracted from the National Health Commission of the People's Republic of China (http://www.nhc.gov.cn/wjw/yqbb/list.shtml). Given that seasonal fluctuating trends in respiratory infectious diseases might bias the true variability, we removed seasonality by averaging over the same month each year from the data to focus on fluctuations in the data trends. As shown in the following functions, it is a function of month and is independent of year.
In this function, the N (y, m) is the number of new cases in the year (y) and the month (m). The adjusted series will be . Following seasonal adjustment, we conducted t-test or rank-sum test to investigate differences in the adjusted number of new cases before and after the COVID-19 outbreak. Otherwise, the absolute growth rate was also calculated to eliminate misinformation caused by flaws in the annual report. Data analysis and visualization were performed with Python software.
The shape of the curve showed that the overall trends for measles and mumps were broadly similar. Compared to previous years, the curve flattened out after sharply declining from 2020 onwards. The number of reported cases of measles increased significantly between March and June, while mumps increased significantly between May and June and between November and December each year. No change in the peak measles and mumps period was observed before and after the emergence of SARS-CoV-2. Measles cases were reported on average 409 cases per month from 2017 to 2019, whereas average 96 cases per month were reported from 2020 to 2022. Given the non-normality of the data, we used the Mann-Whitney U test to compare the seasonally-adjusted data. Results from the analysis of the number of positive measles infections revealed a significant difference in the number of measles infections before and after the COVID-19 outbreak in mainland China (Fig. 1A and 1B; Mann-Whitney U test: P < 0.0001). As for mumps, positive cases were reported on average 22,761 cases per month from 2017 to 2019, while average 11,161 cases per month were reported from 2020 to 2022. Compared to the number of monthly cases from 2017 to 2019, there was a statistically significant difference in the decrease in cases from 2020 to 2022 (Fig. 1C and 1D; t-test: P < 0.0001).
Fig. 1The monthly new cases of measles and mumps before and after the COVID-19 pandemic. A) the raw monthly new cases of measles (solid line) and the seasonal component (dash line) in the upper panel, and the residual after removing the seasonal component in the lower panel. B) the residual distributions of measles before (black) and after (red) the COVID-19 pandemic. They illustrated that the COVID-19 pandemic decreased the number of new cases significantly (P < from the Mann-Whitney U test on the two distributions in Fig. 1B). C) the raw monthly new cases of mumps (solid line) and the seasonal component (dash line) in the upper panel, and the residual after removing the seasonal component in the lower panel. D) the residual distributions of mumps before (black) and after (red) the COVID-19 pandemic. They illustrated that the COVID-19 pandemic decreased the number of new cases significantly (P < from the student's t-test on the two distributions in Fig. 1D).
Interestingly, the monthly average of mumps infections went from 21,233 to 25,259 between 2017 and 2020 compared to the previous two years (Table 1), and peaked in June 2019. However, the number of cases decreased following the implementation of the COVID-19 restrictions in January 2020. Moreover, compared to the previous year, the number of measles and mumps infections both indicated the most decrease in the absolute growth rate in 2020 (Table 1). Measles cases reported in 2020 decreased by 65.4%, while mumps decreased by 56.8%. The decrease in 2021 was not as obvious as in 2020, which might be related to the relaxation of the full intervention policy in mainland China in 2021. Anyway, in comparison to 2018 to 2019, measles was reported 77.3% lower and mumps 55.4% lower in 2020 to 2021. The fluctuation of the absolute growth rate was more pronounced for measles than that for mumps, which might be due to the fact that the effectiveness of NPI in lowering the reproductive rate of infection depended heavily on the underlying pre-intervention reproductive rate.
Table 1The absolute growth rate of measles and mumps diseases in Mainland China from 2017 to 2021.
Overall, the present study based on seasonality-adjusted values showed that the number of measles and mumps infections decreased during the COVID-19 pandemic compared to the previous period, which was consistent with recently published studies about other human respiratory infections.
In the mainland China, interventions taken by the government to control the COVID-19 pandemic, including temporary lockdowns, wearing of masks, social distancing, enhanced personal hygiene and reduced travel, can be effective in preventing the infection of other respiratory infectious diseases which share the same transmission route. In addition, according to this policy, all patients presenting with fever and respiratory symptoms are advised to attend hospital for screening if there are no contraindications. It might lead to a significant increase in the proportion of patients newly diagnosed with measles and mumps. Therefore, we suggest that this reduction could be explained by the NPI implemented in mainland China during the COVID-19 pandemic.
In short, our present findings demonstrate that the number of reported cases of measles and mumps is related to the intervention strategy. NPI plays a positive role in the prevention and control of the prevalence of these common respiratory infectious agents.
References
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Impact of non-pharmaceutical interventions targeted at COVID-19 pandemic on influenza burden - a systematic review.
MMWR Morb Mortal Wkly Rep.2021; 70 (Nov 12PubMed PMID:34758014. Pubmed Central PMCID: PMC8580203 Journal Editors form for disclosure of potential conflicts of interest. Matt Ferrari reports grants from the Bill and Melinda Gates Foundation, the World Health Organization (WHO), and Gavi, the Vaccine Alliance, to develop measles models and travel support from WHO to attend the Strategic Advisory Group of Experts on Vaccines (SAGE) meeting in 2019 and the Measles and Rubella SAGE working group. Allison Portnoy reports grant support from The Pennsylvania State University for time and analytic contributions to this manuscript. No other potential conflicts of interest were disclosed. Epub 2021/11/11. eng): 1563-1569
☆Author contributions: Haiyan Yang, Fang Liu and Guangcai Duan designed the study. Jie Xu and Yujia Wang conducted data collection. Jie Xu conducted statistical analyses. Jie Xu wrote the manuscript. All the authors approved the final version of the manuscript.
☆☆Funding: This study was supported by the grant from National Natural Science Foundation of China (No. 82273696). The funder has no role in the data collection, data analysis, preparation of manuscript and decision to submission.
☆☆☆Conflicts of interest statement: The authors declare that they have no any potential conflict of interest regarding this submitted manuscript.
☆☆☆☆Data availability statement: The data that support the findings of this study are included in this article and available from the corresponding author upon reasonable requests.
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