1. Introduction:
Severe Acute Respiratory Coronavirus 2 (SARS-CoV-2), a newly identified coronavirus with size of 60–140 nm similar to SARS-CoV (approximately 80% similar), caused the most severe pandemic disorder of 21st century called COVID-19 1,2. SARS-CoV-2 attaches to Angiotensin Converting Enzyme 2 (ACE2) receptor with 10–20 folds higher affinity than SARS-CoV 3. Today, massive antibiotic therapy is considered for some COVID-19 patients that result in more susceptibility to subsequent infections4; one of the most irritant complications is antibiotic-associated diarrhea 5. In this situation, probiotics may be a reasonable choice; they were defined as “Live microorganisms which when administered in adequate amounts confer a health benefit to the host” 6. on the other hand, Probiotics have shown useful effects on treatment and prevention of viral infections 7 due to the proven immunomodulatory activity and ability to stimulate interferon production; gut–lung axis explains the possible relations between respiratory disorders and gut microbiome 8.
Recently, some COVID-19 patients showed microbial dysbiosis with decreased Lactobacillus and Bifidobacterium9. Several different probiotics, includingLactobacillus acidophilus, Bifidobacterium andSaccharomyces boulardii , along with minerals & vitamins were given to a COVID-19 case; this type of nutritional support lowered the complication of massive antibiotic therapy 10. As well, COVID-19-like symptoms disappeared after two days administration of oral probiotic in a 9 years-old boy 11. Results of a case series consist of 62 SARS-CoV2 infected patients in Zhejiang province were interesting; probiotics were administered as adjunct12. Other reports showed significant effect of probiotics; Compared to patients with non-severe disease, patients with severe disease had significantly more frequency to receive probiotics tablets (87.5% vs 40.4%, p=0.037) 13. Results from another research suggested concurrent use of probiotics in COVID-19 patients to decrease the risk for Candida albicans (caused by prophylaxis with azithromycin) 14.
Up to April 2020, two clinical trials have been registered regarding the probiotics supplementation in COVID-19 patients 15, however, more information is needed for designing research protocols. We tried to summarize the possible relationships between probiotics and viral infections especially SARS-CoV-2-related literature in this systematic review.