Currently, the world is facing the COVID-19 epidemic, a disease caused by SARS-CoV-2. Emerging body of molecular evidences suggested a similar path to SARS and MERS viruses. A viral particles cascade enters into the human body through eyes, nose, and mouth, few of these viral particles reaches to the lower respiratory tract through breathing and here their spike protein act like a key and lock into epithelial cells which are the air sacs in lungs. SARS-CoV-2 is undetectable for a longer period of time than many other flu and coronaviruses. Once they entered inside body, they overtake the cell’s machinery, replicate, multiply and infect the adjoining cells. All the viruses have a tell-tale signature on the surface known as antigens, identifying these antigens is what activate the immune system by producing the antibodies. Researchers have shown that a wide range of immune cells that react to SARS-CoV-2 and helps in recovery could be helpful in the development of potential vaccines.

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.

Psoriasis is a multi-systemic chronic autoimmune inflammatory disorder affecting 125 million people worldwide. The most common type of psoriasis is plaque psoriasis affecting up to 90% of the patients and is characterized by well-demarcated, symmetric, and erythematous plaques with overlying silvery scales that may be painful or itchy. Psoriasis may also affect the joints; increase the risk of developing metabolic syndrome, diabetes, Crohn’s disease, ulcerative colitis, uveitis, certain cancers and an increase in the risk of cardiovascular diseases. Both the skin and the gut microbiome can modulate the development and progression of psoriasis. A connection between the microbiome and immunological mechanisms are antimicrobial peptides, which regulate the microbiome at interfaces and, as antigens, can trigger psoriasis. Few studies were conducted to demonstrate the effect of probiotics on different diseases, as they are living microorganisms that confer a health benefit when administrated in adequate amounts. The effects of administering probiotics include the stabilization of the gut bacterial community and the restoration of “signature” of bacterial microbiota, which is a result of lowering the pH, producing bacteriocins, altering microRNA (miRNAs), competing with pathogens for certain nutrients and improving the gut barrier function. Probiotics counter weight aggressive commensals in the body and reinforce the barrier function of the epithelium while also contributing to the regulation of innate and adaptive immune responses of the host under healthy or pathogenic conditions. Several clinical trials were conducted based on those findings to examine the role of probiotics in psoriasis, but till now there is no evidence of their efficacy.

Since the first outbreak of SARS-CoV2, Severe Acute Respiratory Syndrome Coronavirus-2 in Wuhan, China in the December 2019, the world continues to be in state of fear, uncertainty, tension and anxiety till date and this state might continue because of emerging mutants. The vaccination drive all over the world is continuing, still the new variants are cause of concern, with the aim to prevent the spread of the virus, focus should be on techniques and processes which helps in strengthening our defense mechanism, the immune system. It has becoming clear from several studies that the immune system is greatly impacted by the COVID-19 infection through several inflammatory reactions. The role of balanced diet full of nutrients cannot be overlooked in controlling infectious diseases. A balanced diet which should include plant foods, vitamins and micronutrients and this review wants to emphasize on the preventive role played by the plant foods, vitamins and minerals in COVID-19 infections, to reduce the mortality rate as well as the morbidity in patients who are infected.

Mucormycosis or black fungus although a rare fungal infection but has potential to be lethal and thus requires immediate treatment. The immune system is weakened due to SARS-CoV-2 and the body becomes susceptible and vulnerable to other infections as people are immune compromised. The immune system becomes weakened due to COVID-19 treatment especially in patients who are taking steroids making the body prone to attack by black fungus. As the black fungus cases are increasing in India, the country is facing shortage in medicaments in face of dual crisis. An epidemic of black fungus is sweeping India in the wake of a severe surge in COVID-19 cases. Experts are of the opinion that the cause is a combination of factors. These factors might include contaminated oxygen equipment and use of steroid drugs to treat certain COVID-19 patients.