key: cord-0821750-luloic87
authors: Itaya, Takahiro; Furuse, Yuki; Jindai, Kazuaki
title: Does COVID-19 infection impact on the trend of seasonal influenza infection? 11 countries and regions, from 2014 to 2020
date: 2020-05-31
journal: Int J Infect Dis
DOI: 10.1016/j.ijid.2020.05.088
sha: bd998ca09342507dc7357fd68d93374b335058cd
doc_id: 821750
cord_uid: luloic87

Abstract Objectives Infection due to the 2019 novel coronavirus disease (COVID-19) is widespread dramatically around the world. This COVID-19 pandemic could increase public concern to prevent infectious disease. The present study aimed to assess the relationship between the COVID-19 epidemic and decreasing another infectious disease. Methods This study was performed to show trends in seasonal influenza cases from the 2014–2015 season to the 2019–2020 season in 11 countries and regions, and evaluate whether the trends in the 2019–2020 season were different before and after the COVID-19 pandemic compared to previous seasons using a quasi-experimental difference-in-difference design. Results In East Asia, the number of seasonal influenza cases in the 2019–20 season was lower after the COVID-19 transmission compared to previous years. However, this was not the case in the American countries or in European countries. Conclusion The COVID-19 epidemic might have altered health behaviors, resulting in an unexpected reduction of seasonal influenza cases.

The number of people infected with the 2019 novel coronavirus disease (COVID-19) has surged worldwide since the first case of COVID-19 was reported in December 2019 in Wuhan, China [1] . COVID-19 has been featured extensively in both traditional and social media, leading to high levels of attention on previously unknown respiratory disease and risk perception among the public [2] . Moreover, infection prevention and control strategies to help prevent the spread of COVID-19 in community settings have aligned with those used for other common respiratory J o u r n a l P r e -p r o o f viral infections such as influenza infection; such strategies have included hand hygiene, cough etiquette, and avoiding close contact with sick persons [3] . We aimed to identify the relationship between the COVID-19 pandemic and the incidence of seasonal influenza in different regions and countries.

The subjects resided in the following 11 countries and regions: Northern . Of note, the Chinese healthcare authorities officially reported human-to-human transmission on January 20, 2020 [4] . Therefore, we operated on the assumption that public concern presumptively derived from the COVID-19 epidemic affected the incidence of influenza after January 20, 2020 (EPI week 4). 

Since Hong Kong, Japan, and Taiwan are geographically proximal to China, the impact of the COVID-19 outbreak in China might have impacted the public more directly in these countries than in other countries. Hong Kong, Japan, and Taiwan reported imported cases from China in the evolving phase of the COVID-19 outbreak, and public concern about the COVID-19 outbreak could have risen dramatically as a result [1] . The citizens of these areas might have taken robust preventive measures, including wearing masks, hand hygiene, and even selfimposed physical distancing. Consequently, these precautionary measures may have helped to prevent influenza transmission.

We propose that not only geographic differences but also cultural differences could have enhanced self-protective rituals. For instance, although the effect of wearing face masks on virus transmission is unknown [5] , people in Asian regions routinely wore masks in public even before the COVID-19 outbreak, whereas this practice was not commonly seen in the US or in European countries [6, 7] . In addition, norms concerning interpersonal distance, hugging, 

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