Iodine and Selenium as Antiviral Agents: Potential Relevance to SARS-CoV-2 and Covid-19

Abstract

Iodine and selenium are linked through their effects on thyroid function. Both also have anti-viral properties relevant to SARS-CoV-2 infection. In the form of povidone-iodine solution, iodine is a virucidal agent that has been shown in vitro to kill the coronaviruses SARS-CoV and MERS-CoV, implicated in previous coronavirus epidemics. Viral loads of SARS-CoV-2 are high in the nasal cavity, nasopharynx, and oropharynx. Under in-vitro conditions mimicking nasopharyngeal secretions, povidone-iodine solution significantly inactivated SARS-CoV-2, hence some health-care workers in intensive-care units, dental treatment or maxillofacial surgery are using topical povidone-iodine solution, at 0.5%. However, those using topical povidone-iodine solution prophylactically over a period of months might experience adverse effects on thyroid function from exposure to excess iodine, particularly if they have insufficient intake of selenium. Selenium has a protective function on the thyroid; on exposure to excess iodine, too much hydrogen peroxide is produced which is removed by a selenoprotein, glutathione peroxidase. In addition to its protective function on the thyroid, selenium is acknowledged, independently, to combat a number of viral diseases. Observational studies have associated higher selenium status with better recovery from COVID-19 and poorer selenium status is associated with COVID-19 death. In-vitro evidence shows that SARS-CoV-2 reduces the expression of selenoproteins that protect against viral disease. It is therefore advisable to ensure adequate selenium intake, particularly in countries with low or marginal selenium status. Finally, for those using povidone-iodine prophylactically in such countries, a modest oral supplement of selenium, such as 100 μg/d, might be advisable.