Prevalence and clinical relevance of viraemia in viral respiratory tract infections: a systematic review

In this Review, we analysed the prevalence of viraemia during infection with SARS-CoV-2 and other relevant respiratory viruses, including other human coronaviruses such as MERS-CoV and SARS-CoV, adenovirus, human metapneumovirus, human rhinovirus/enterovirus, influenza A and B virus, parainfluenza virus, and respiratory syncytial virus. First, a preliminary systematic search was conducted to identify articles published before May 23, 2024 that reported on viraemia during infection with respiratory viruses. The articles were then analysed for relevant terms to identify the prevalence of viraemia, its association with the disease severity and long-term consequences, and host responses. A total of 202 articles were included in the final study. The pooled prevalence of viraemia was 34% for SARS-CoV-2 and between 6% and 65% for other viruses. Association of viraemia with disease severity was extensively reported for SARS-CoV-2 and also for SARS-CoV, MERS-CoV, adenoviruses, rhinoviruses, respiratory syncytial virus, and influenza A(H1N1)pdm09 (albeit with low evidence). SARS-CoV-2 viraemia was linked to memory problems and worsened quality of life. Viraemia was associated with signatures denoting dysregulated host responses. In conclusion, the high prevalence of viraemia and its association with disease severity suggests that viraemia could be a relevant pathophysiological event with important translational implications in respiratory viral infections.