1 Introduction
Since a cluster of coronavirus disease 2019 (COVID-19) cases were first reported in Wuhan, China, in December 2019, it has become a global threat and spread rapidly across more than 200 countries and regions (WHO, 2020). A striking aspect of COVID-19 is that the disease became a pandemic in several months, resulting in over 16 million cases and 600 thousand deaths worldwide as of 30 July (WHO, 2020). Although we learned more about COVID-19 and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the past several months depending on the modern advanced technology, some issues, such as a useful strategy to prevent disease spread, transmission route, and effective treatments, have been still severe challenges until now. Additionally, the possibility of co-infection with other respiratory pathogens remains unclear. This should be an important concern for clinicians in the management of COVID-19.
Generally, co-infection has been already detected during the epidemic of previous emerging infectious diseases, including severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). Previous serological evidence revealed that the incidences of acute or recent Chlamydophila pneumonia (CP) or Mycoplasma pneumonia (MP) infection in SARS patients were 30% and 9%, respectively (Zahariadis et al., 2006). In Hong Kong, a major nosocomial outbreak of SARS revealed co-infection of human metapneumovirus (MPV) (Lee et al., 2007). Moreover, co-infection of Middle East respiratory syndrome coronavirus (MERS-CoV) with influenza has been reported, and it demonstrated that 18% critically ill patients with MERS-CoV had bacterial co-infection, followed by 5% with viral co-infection, in a multicenter retrospective cohort study (Alfaraj et al., 2017; Arabi et al., 2017). However, there is limited data regarding co-infection of other respiratory pathogens in COVID-19 patients, as well as the impact of co-infection on COVID-19 prognosis.
It is considered that the recognition of SARS-CoV-2 infection is important as it enables the implementation of appropriate infection control measures and possible promising antiviral therapy, but clinicians should not neglect the possibility of SARS-CoV-2 co-infection (Lai et al., 2020). Therefore, we aim to expand the knowledge of distribution and associated factors of co-infection in COVID-19 patients, and assess the impact of co-infection on COVID-19 prognosis.