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Letters to the Editor

Coinfection of Influenza Virus and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-COV-2)

Wu, Di MMed; Lu, Jianyun MMed; Ma, Xiaowei MMed; Liu, Qun MMed; Wang, Dedong MMed; Gu, Yuzhou MMed; Li, Yongguang BSc; He, Weiyun BSc

Author Information
The Pediatric Infectious Disease Journal: June 2020 - Volume 39 - Issue 6 - p e79
doi: 10.1097/INF.0000000000002688
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To the Editors:

Coronavirus disease 2019 (CoVID-19) is a new infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which originated from Wuhan in China and has now spread globally. However, despite the concern focused on SARS-CoV-2, influenza virus continues to circulate and cause disease. Here we report a mixed infection. Physicians should be alert that a positive test for influenza does not rule out the possibility of COVID-19 disease.

The SARS-COV-2 outbreak in late December of 2019 in Wuhan, China, has caused many infections and deaths globally. SRAS-COV-2 is a new respiratory tract transmitted disease mainly through respiratory droplet and close contact, aerosol but fecal-oral route is also suspected. As of March 19, 2020, a total of 23,473 cases, and 9840 deaths were reported.1

In China, several respiratory viruses are also now active including influenza, parainfluenza virus, respiratory syncytial virus, adenovirus, and now SARS-COV-2. Unfortunately, according to the World Health Organization influenza website,2 the respiratory illness indicators and influenza activity remained elevated overall in the northern hemisphere which are in a “flu” season. The weekly report of the influenza surveillance reported that the United States now has its highest pneumonia and influenza mortality since 2004, except for the 2009 pandemic.3 During the SARS pandemic in 2003, Yang et al4 found that the patients with fever, cough or sore throat had a 5% of influenza virus positive rate, and with SARS infection reportedly increasing at the meantime. This raises the concerns that there might be mixed infections of seasonal influenza and the novel coronavirus. Thus, we do think there might be a change of mixed infection of the influenza virus and SARS-COV-2. The Chinese experts from China-Japan Friendship Hospital have reported a case coinfection with influenza A virus and SARS-CoV-2.5 So, in an era when testing for COVID-19 is in short supply in many areas of the world, when patients have a positive test for influenza, one cannot assume that they do not also have SARS-CoV-2 infection. Measures should be taken to enhance the respiratory infectious diseases surveillance systems and screen the people with fever, cough or sore throat for both viruses with oral, nasopharyngeal and anal swabs.

Di Wu, MMed
Jianyun Lu, MMed
Xiaowei Ma, MMed
Qun Liu, MMed
Dedong Wang, MMed
Yuzhou Gu, MMed
Yongguang Li, BSc
Weiyun He, BSc
COVID-19 Emergency Response Unit, Guangzhou Center for Disease Control and Prevention, Guangzhou, People’s Republic of China


1. World Health Organization. Coronavirus disease 2019 (COVID-19) Situation Report – 60, March 19. 2020. Available at: Accessed March 21, 2020.
2. World Health Organization. Influenza update - 362, based on data up to 16 February. 2020. Available at: Accessed March 17, 2020.
3. Centers for Disease Control and Prevention. Weekly U.S. Influenza Surveillance Report, Key Updates for Week 8, ending February 22. 2020. Available at: Accessed March 19, 2020.
4. Yang W, Lu E, Zhou X, et al. Influenza virologic and epidemiologic surveillance in Guangzhou, 2003. South China. J Prev Med. 2005;31:10–13.
5. Wu X, Cai Y, Huang X, et al. Co-infection with SARS-CoV-2 and influenza A virus in patient with pneumonia, China. Emerg Infect Dis. 2020;26. [Epub ahead of print].
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