The Impact of Anti-Epidemic Measures Against Coronavirus Disease 2019 (COVID-19) on the Seasonal Influenza Epidemic
The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for coronavirus disease 2019 (COVID-19), in late 2019 marked the beginning of a global health crisis. On March 11, 2020, the World Health Organization (WHO) declared the outbreak a pandemic. By March 18, 2020, the number of laboratory-confirmed COVID-19 cases had surpassed 200,000 worldwide. In response, many countries implemented unprecedented anti-epidemic measures to curb the spread of the virus. These measures, while primarily aimed at controlling COVID-19, also had significant effects on other respiratory infections, particularly the seasonal influenza epidemic.
Both influenza viruses and coronaviruses are respiratory pathogens that share similar routes of transmission and related pathogenesis. The timing of the COVID-19 outbreak coincided with the seasonal influenza epidemic in the Northern Hemisphere, providing a unique opportunity to assess the effectiveness of public health interventions. By analyzing data from the WHO’s FluNet-CHARTS, which provides weekly updates on confirmed influenza cases in various countries, researchers have been able to evaluate the impact of anti-epidemic measures on the influenza epidemic.
In China, the peak of the influenza epidemic occurred in the second week of 2020, with over 7,000 cases reported weekly. On January 25, 2020, the Chinese government tightened anti-epidemic measures in response to the COVID-19 outbreak. By the seventh week of 2020, the influenza rate in China, a country with a population of 1.4 billion, had dropped to levels typical of the inter-epidemic period, with fewer than 400 cases per week. By the eighth week, the number of influenza cases had fallen below the background level, with fewer than 20 cases reported weekly. This dramatic decline in influenza cases demonstrates that China’s efforts to control COVID-19 also effectively mitigated the seasonal influenza epidemic.
In South-West Europe, the influenza epidemic peaked in the fifth week of 2020, with 8,500 cases detected weekly. By the eleventh week, only 20 confirmed influenza cases were reported, representing a 99.8% reduction compared to the peak. Similarly, in North America, the influenza epidemic peaked in the fifth week of 2020, with 30,000 cases detected weekly. By the eleventh week, the number of confirmed influenza cases had dropped to 2,500, representing an 91.7% reduction from the peak. These data indicate that the anti-epidemic measures implemented in these regions had a significant impact on the influenza epidemic, although the measures were less effective in controlling the spread of COVID-19.
The differential impact of anti-epidemic measures on COVID-19 and influenza can be attributed to several factors. In China, the rapid and stringent implementation of containment measures, including widespread testing, contact tracing, and quarantine, effectively halted the spread of both COVID-19 and influenza. In contrast, the delayed and less comprehensive measures in South-West Europe and North America were less effective in controlling COVID-19, although they still had a substantial impact on the influenza epidemic.
The WHO data underscore the potential of anti-epidemic measures to control not only COVID-19 but also other respiratory infections, including influenza. The experience of the 2020 influenza epidemic suggests that timely and coordinated public health interventions can significantly reduce the spread of respiratory viruses. This is particularly relevant given the ongoing threat of emerging respiratory viruses, including highly pathogenic influenza viruses. The 1918 influenza pandemic, which caused widespread morbidity and mortality, serves as a stark reminder of the potential consequences of a new influenza pandemic.
In light of these findings, it is essential to develop a concerted strategy for responding to the emergence of new respiratory viruses. Existing preparedness programs for influenza pandemics, which have been developed in many countries, can serve as a foundation for such a strategy. Additionally, the Global Influenza Surveillance and Response System (GISRS), which has been operational since 1952, provides a robust framework for monitoring and controlling emerging respiratory viruses. GISRS comprises over 150 centers worldwide, equipped with the necessary laboratory capacities to detect and respond to new respiratory pathogens.
The experience of the 2020 influenza epidemic also highlights the importance of international cooperation in addressing global health threats. The rapid spread of COVID-19 across borders underscores the interconnectedness of the modern world and the need for coordinated action to prevent and control pandemics. By sharing data, resources, and expertise, countries can enhance their ability to respond to emerging respiratory viruses and mitigate their impact on public health.
In conclusion, the anti-epidemic measures implemented in response to the COVID-19 pandemic had a significant impact on the seasonal influenza epidemic in 2020. The data from China, South-West Europe, and North America demonstrate that timely and stringent public health interventions can effectively reduce the spread of respiratory viruses. However, the differential impact of these measures on COVID-19 and influenza highlights the need for a coordinated and comprehensive approach to pandemic preparedness and response. By building on existing frameworks such as GISRS and leveraging international cooperation, the global community can enhance its capacity to address the ongoing threat of emerging respiratory viruses.
doi.org/10.1097/CM9.0000000000001344
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