Study aim: Determine the effect of NBS powder on immune system function and clinical manifestations in patients with COVID-19 Design: The randomized clinical trial, parallel groups, 23 patients will be enrolled in each arms of the study. Settings and conduct: This study will be performed in Sina hospital, Hamadan, Iran. In this study 46 patients selected based on inclusion and exclusion criteria will be divided into two groups (23 in each group) by simple randomization. Patients in control group will be prescribed standard regimen for COVID-19. Patients in intervention group in addition to the standard antiviral treatment of the two-drug regimen, NBS powder will be taken at a dose of 2 g / day for 4 weeks. Participants/Inclusion and exclusion criteria: The confirmed COVID-19 patients through PCR over the age of 20 year and is not allergic to the powder used. Intervention groups: In the intervention group, in addition to the standard antiviral treatment of the two-drug regimen, NBS powder will be taken at a dose of 2 g / day for 4 weeks. The control group will only receive standard antiviral treatment with a two-drug regimen. Main outcome variables: Improve clinical signs and strengthen the immune system