Intervention characteristics.

<div><p>Background</p><p>Gut microbiota play important roles in several diseases like viral infections. In this systematic review, our objective was to assess the efficacy and safety of fecal microbiota transplantation (FMT) in treating various viral diseases.</p><p>Methods</p><p>We conducted searches on databases including PubMed, Web of Science, Scopus, and Google Scholar until November 2023. Clinical trials reported outcomes related to safety of FMT or its efficacy in patients with viral diseases were included. We excluded other types of studies that enrolled healthy individuals or patients with other disorders and did not use FMT. The assessment of bias risk was conducted using the National Institutes of Health (NIH) study quality evaluation tool.</p><p>Results</p><p>Eight studies with total 196 participants were included. Viral diseases were human immunodeficiency virus (HIV), hepatitis B, COVID-19 and Clostridioides difficile coinfection, and cytomegalovirus colitis. In hepatitis B cases, HBeAg clearance was significant in those received FMT (p<0.01), while it was not significant in another one (p = 0.19). A clinical response was noted in 37.5% of patients with cytomegalovirus colitis, with an equal percentage achieving clinical remission post-FMT. There was a significant reduction in Clostridioides difficile relapse rate in FMT group than controls in coinfection of Clostridioides difficile and COVID-19 (2.17% vs. 42.5%, p<0.05). In patients with HIV, partial engraftment of the donor microbiome and increases in alpha diversity were observed after FMT. No severe adverse events were reported. Most studies had fair or good qualities.</p><p>Conclusions</p><p>Our findings revealed FMT as a promising, safe treatment for some viral diseases. It improved viral clearance, clinical outcomes, and inflammation. However, the varying responses and small sample sizes call for more trials on FMT in viral diseases.</p></div>