Discussion
Viruses co-infection were usually seen in the influenza epidemic and pandemic (Goka, Vallely, Mutton, & Klapper, 2013;Meskill, Revell, Chandramohan, & Cruz, 2017). Goka et al found that IAV and influenza B virus co-infection was associated with a significant increase in risk of admission to ICU or death, whereas co-infection with IAV and other viruses significantly increased the risk of admission to a general ward (Goka et al, 2013). In the COVID-19 pandemic, we found some patients were co-infected with SARS-COV-2 and IAV but we did not know much more about the two viruses’ co-infection. To better understand the clinical course of SARS-COV-2 and IAV co-infection, we performed a fast review on patients infected with the two viruses.
In this review, we collected 13 patients co-infected with SARS-COV-2 and IAV in China, Japan, Iran and America (Azekawa et al, 2020;Ding et al, 2020;Khodamoradi et al, 2020;Konala et al, 2020;Sha, 2020;Wu et al, 2020). In the 13 patients, the propotion of sever type was 53.8% (7 cases), which was much higher than that in COVID-19 (Guan et al, 2020), indicating co-infection with SARS-COV-2 and IAV resulting in more severe condition. IAV infection was more common in children and old people (Thompson, 2004), while we only found one child suffering from SARS-COV-2 and IAV co-infection in our cohort (Sha, 2020). Similar to the COVID-19 patients, the patients co-infected with SARS-COV-2 and IAV also manifested symptoms such as fever, cough, dyspnea and myalgia etc. However, in this review, we found 10 of 13 patients (76.9%) had dyspnea on admission, higher than that reported by Wang and Huang et al (31.2% and 55% respectively) (Huang et al, 2020;Wang et al, 2020). This may remind us that COVID-19 patients co-infected with IAV may develop a more severe disease in lower respiratory tract. The median time of hospital stay in this review was 17 days (IQR,15-20), similar to the finding (median, 18 days, IQR, 14-27) reported by Xu et al (Xu et al, 2020). The reason why patients co-infected with SARS-COV-2 and IAV developed more severe clinical condition while had similar hospital stay need further research. All the patients had typical abnormal radiological changes and 7 of 13 patients (53.8%) had lower lymphocyte count on admission, which could indicate viral infection but could not tell the pathogens relying on these signs.
In this review, we found 8 of 9 patients (88.9%) were treated with oseltamivir, a neuraminidase inhibitor recommended to deal with influenza by the European Union and the USA(European Centre For Disease Control, 2017; Centers for Disease Control and Prevention), and 8 of 8 patients received antibiotic therapy to prevent secondary bacterial infection(McCullers & Bartmess, 2003). But whether oseltamivir has some effect on SARS-COV-2 viral shedding and whether co-infection with SARS-COV-2 and IAV will cause secondary infection need further investigation. Three patients were treated with corticosteroids, while corticosteroids were not usually recommended in the COVID-19 pandemic concerning about the possible side effects of corticosteroids on virus clearance and association with high rates of complications (Arabi et al, 2018;Stockman, Bellamy & Garner, 2006). 7 patients were cured and discharged from hospital while 6 patients did not have detailed information on clinical course.
We noticed the patients co-infected with SARS-COV-2 and IAV accounted for a small proportion in the COVID-19 pandemic (Kim, Quinn, Pinsky, Shah, & Brown, 2020;Nowak, Sordillo, Gitman, & Paniz Mondolfi 2020). This may due to the interference between viruses (Schultz-Cherry, 2015), and SARS-COV-2 took the dominated place in the pandemic. The mechanism of how SARS-COV-2 and IAV interfere each other deserves further study.
Our study has some limitations: first and most, though this was a fast review, our samples were extremely small due to the rare reports on SARS-COV-2 and IAV co-infection. Second, we could not collect detail information about each patient because some information was not available and whether the missing information may have some influence on our results was unknown. Third, the reports did not provide SARS-COV-2 viral shedding time, thus whether co-infection with IAV have some influence on SARS-COV-2 viral shedding remains unknown. Fourth, we could not identify which virus was first infected, which may contribute to account for the co-infection course. Finally, no patient got lower respiratory tract samples for detection for SARS-CoV-2 and IAV in this review, so whether the two viruses were both involved in the pathological progression of pulmonary could not be identified. However, this review highlights that we should pay attention to the problem of co-infection of two or more respiratory pathogens. The association between the occurrence of co-infection and substantially higher severity of disease deserves further study, but a rapid and proper diagnostic of wide spectrum of viral respiratory pathogens reveals an accurate picture of the disease and is essential for appropriate therapeutic management and control of infection.