A method to treat nasal tissue reduces the ability of a virus to infect a human being. The method comprises the steps of providing a liquid composition comprising water, a humectant, a foam builder, 0.01% to 9% by weight of a surfactant, and a minor effective quantity of thickener to produce a coating on the nasal tissue after the liquid composition is applied to the nasal tissue as a foam; applying the liquid composition to the nasal tissue as a foam; and, allowing bubbles in the foam to dissipate so that a coating forms on the nasal tissue.