Iodine circulating in the blood is captured by numerous tissue sites and ends up in mucus secretions. These tissues include the salivary glands, nasal secretions, lungs and stomach. Tissues and mucus products containing iodine defend against invasion by bacteria and viruses. Respiratory and oral transmission are key pathways for viral infections. With enough supplementation, iodine can be ever-present and ready to defend in both the upper- and lower-respiratory systems as well as in the stomach.