The SARS-COV-2 rapid spread caused an international public health emergency with unprecedented rates of morbidity and mortality. Post COVID-19 condition occurs as a spectrum of symptoms that present four or more weeks after acute infection with SARS-CoV-2. Most published data to date state 50-70% of hospitalized patients experienced at least one post-acute COVID-19 symptom up to 3 months after discharge. Commonly reported symptoms include; neurocognitive post COVID-19 (fatigue, dizziness, inattention, and brain fog), respiratory post-COVID (dyspnea, chest pain, and cough), and mental health related symptoms (insomnia, depression, and post-traumatic stress disorder). Additionally, gastro-intestinal post COVID-19 (diarrhea, vomiting, and abdominal pain) along with decline in quality of life and decreased ability to perform activities of daily living were reported. The response to post COVID-19 symptoms is still in its infancy despite being an emerging crisis as scientific evidence and robust data are nonetheless required for clear definition, identification of time frame, classification and management of the condition. New studies are needed to identify total and individual incidence/prevalence rates of different clinical presentations of post COVID-19 symptoms. These future studies will help us to o improve early recognition of long term symptoms after acute infection of COVID-19.

Probiotics, prebiotics, and synbiotics modify various aspects of local and systemic immune function in multiple experimental models. However, their impact and mechanisms of action are not known across all products or noticed in every population studied, and impacts on in vitro, ex vivo, or other measures of immune function do not necessarily result in an impact on infection and illness in vivo. Studies have discussed that intestinal microbiota has an essential role in enhancing the immune system against viruses. The regulatory impact of the intestinal microbiota on viral infection is connected with local and systemic immune responses and plays a part in congenital and adaptive immune responses. The microbiota composition critically modulates the production of virus-specific CD4 and CD8 T cells and antibody responses following influenza virus infection. The intestinal microbiota has an important role in the stabilizing of immune homeostasis by augmenting the integrity of the barrier functions of the gut mucosa, which is a crucial aspect of systemic immunity. In conclusion, the intestinal microbiota can influence organismal immunity locally and systemically, proximally, and distally. Studying the possible mechanism by which the intestinal microbiota maintains host immunity can provide a clearer understanding of the occurrence and development of diseases.