Discussion
SARS-CoV-2 and influenza infection are associated with respiratory
disorders, and signs in patients can vary from moderate to severe
morbidity and mortality (30). Some studies and case reports indicate
that influenza co-infection with COVID-19 may be important for the
infected patient’s severity (31-34). In this study, the prevalence of
co-infection SARS-CoV-2 with influenza A and B, clinical
characterization, and chest radiography in co-infected patients with
confirmed SARS-CoV-2 infection was meta-analyzed. The results indicated
that the prevalence of influenza A is higher than influenza B
co-infection in COVID-19 patients (2.3(0.5-9.3) vs. 0.1 (0.4-3.3)). Our
findings show that fever and cough were the most common clinical
symptoms (86% and 46%, respectively) in co-infected SARS-CoV-2
patients with influenza A or B. In addition, Fatigue, Diarrhea, and
Difficult Breathing were the less common clinical findings among
co-infected patients (13.8%, 12.2%, and 9.3%, respectively).
Influenza and SARS‐Cov‐2 viruses are transmitted by contact, droplets,
and contaminated surfaces and cause respiratory diseases with a broad
range of moderate to severe symptoms (35, 36). Based on the basic
reproduction number R zero (R0), SARS‐Cov‐2 viruses can infect more
people than influenza (1.5–5.7 for SARS‐Cov‐2, 0.9–2.1 for influenza)
(36, 37). Several studies have confirmed co-infection of SARS-CoV-2 with
influenza A and influenza B, such as studies in the United States (15,
16), China (17), and Iran (18). Some articles have shown that
respiratory viruses such as influenza can lead to complications of the
disease and even patient death in confirmed cases of COVID-19 (18-20).
Some other research had the contrary view they assume that competitive
advantage in virus connection can play an essential role in SARS-CoV-2
interactions with other viruses, such as influenza, during co-infection
(38, 39). Moreover, different immune response mechanisms can give rise
to a competitive advantage between SARS-COV-2 and other co-infecting
viruses; therefore, in patients with SARS-CoV-2, the co-infection rate
with other viruses, such as influenza, is much lower (38, 39).
The research limitations are the number of studies, small sample sizes,
publication bias, heterogeneity of the study, poor quality analysis and
reporting in some of the included studies.
Due to the low prevalence of SARS-COV-2, co-infected influenza patients,
and many differences between COVID‐19 and influenza, such as
transmissibility, mortality rate, laboratory diagnosis, and clinical
symptoms (30, 40), these results only suggest that consider the
influenza viruses in COVID‐19 suspected patients. As a consequence, this
approach will help to select the best treatment protocol for the
management of COVID-19 patients and reduce the severity of the disease.
People should also be vaccinated against seasonal influenza to reduce
the risk of co-infection in the recent pandemic.