[Viruses protect against asthma].
D001249:Asthma / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control* / Q000821:virology*; D001990:Bronchiolitis, Viral; D002648:Child; D006801:Humans; D006969:Hypersensitivity, Immediate; D015995:Prevalence