Scientists have discovered that nasal cells form the first line of defense against the common cold and work together to block the rhinovirus shortly after infection. The rapid antiviral response of these cells can stop the virus before symptoms appear. If this reaction is weakened or delayed, the virus spreads further. This leads to inflammation and breathing problems. The study thus shows that the body's reaction is more important than the virus itself in explaining why some people get a bad cold and others don't.