Selenium deficiency impairs immune function, increases susceptibility to infections (including HIV and COVID-19), and is linked to cardiovascular diseases such as Keshan disease and myocardial infarction.

There is also evidence that Se deficiency weakens the immune system [9] and affects the proper functioning of the nervous system [10]. ... Se deficiency can cause or induce diseases such as Keshan and Kashin-Beck diseases [35]. Furthermore, Se deficiency is associated with muscle necrosis, hypothyroidism, cardio-cerebrovascular disease, male infertility, increased incidence of various cancer, and an improved immune system [21,36]. Se deficiency has supposed to be linked also to infections such as Coronavirus disease 2019 (COVID-19) and acquired immune deficiency syndrome (AIDS) [37].