Introduction: viral infection of the respiratory tract.
D006801:Humans; D007109:Immunity; D007070:Immunoglobulin A / Q000276:immunology; D012141:Respiratory Tract Infections / Q000276:immunology / Q000382:microbiology*; D014777:Virus Diseases / Q000382:microbiology*; D014780:Viruses / Q000302:isolation & purification
D007070:Immunoglobulin A