Introduction
Coronavirus is a family of RNA viruses that can cause of common cold,
Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory
Syndrome (MERS) with the mortality rate of 10% and 37%, respectively
(1). The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a
novel coronavirus, that causes coronavirus disease 2019 (COVID-19) was
discovered in Wuhan, China and expanded in all over the world from 31
December and spread across the continents (2, 3). The earliest countries
(China, South Korea, and Iran) announced the COVID-19 outbreak as a
public health problem(4).
The coronavirus’s 3000 nucleotide genome encodes four structural protein
such as, Spike (S) protein, Nucleocapsid (N) protein, Membrane (M)
protein, envelop (E) protein and several non-structural proteins (nsp)
(5). Spike (S) protein consist of transmembrane (TM) domain which is
able to bind a host receptor. Nuclear capsid or N-protein which is bound
to the virus single positive strand RNA, is located inside in the
capsid. Nucleoprotein gene plays key role in virus’s replication and
transcription; it allows the virus to hijack human cells and turn them
into virus factories (6). M protein is the most abundant protein in the
viral surfaces which is the central organizer for the virus protein. The
E-protein is a small membrane protein, plays an important role in virus
assembly subunits, membrane penetrance of the host cell and interaction
between viruses and host cells (7).
The symptoms of COVID-19 can include fever, cough, sore throat, fatigue,
shortness of breath and gastrointestinal symptoms such as diarrhea and
nausea (8, 9). Coronaviruses have been responsible for the common cold
by a long time and it is reported that the symptoms of SARS-CoV-2
disease in human is similar to the common cold or influenza; but the
infection and mortality rate of the SARS-CoV-2 is higher than other
respiratory infections. SARS-CoV-2 is a contiguous virus and can be
transmit by the infected person breathed, coughed, or sneezed (10).
Study shows that SARS-CoV-2 may have co-infection with other pathogens
such as viruses, bacteria, and fungi which are related to increase in
hospitalization rate and mortality. It is reported that the most
co-infection occur with influenza virus (11). Influenza is a respiratory
illness with the sign of fever, chills, body aches, sore throats, nasal
congestion, fatigue, vomiting, abdominal pain, and diarrhea, and seems
to have similar transmission character with COVID-19 (12, 13). Recently
study have clarified that there are Immunopathological similarities
between influenza and SARS-CoV-2 (14). Several studies from United Sate
of America (15, 16), china (17) and Iran (18) show that there is
co-infection with SARS-CoV-2 and influenza A and B virus. In addition
some researches indicate that the co-infection of SARS-CoV-2 with
influenza in patients suffering from pneumonia, sinus infection,
bronchitis and cardiovascular disease (CVD) promote the mortality rate
(18-20).
Researchers found that patients admitted to hospital with COVID-19 also
infected with influenza virus. Thus, the current research provides a
better understanding about the control and treatment of co-infection
with SARS-CoV-2 and the influenza virus. So, This study aims to assess
the co-infection of SARS-CoV-2 with influenza among COVID-19 cases.