RESUMO
<p><b>OBJECTIVE</b>To study the application of association rules in Chinese medical pathogeneses and pathologies of heat and phlegm in infantile viral pneumonia.</p><p><b>METHODS</b>Association rules were applied to analyze dynamic changes of heat and phlegm correlated symptoms and signs in 297 infants with respiratory syncytial virus (RSV) pneumonia, thus understanding its evolution or pathogenesis.</p><p><b>RESULTS</b>Heat and phlegm co-exist in infantile viral pneumonia. In their relationship, heat was more likely to affect phlegm, but phlegm was less likely to affect heat. Under the intervention of drugs, the possibility of heat induced by phlegm was gradually reduced. But the possibility of phlegm induced by heat was not obvious as time went by.</p><p><b>CONCLUSIONS</b>Heat and phlegm have a close relationship in the pathogenesis of infantile viral pneumonia. The intervention of drugs could reduce the pathologic evolution of phlegm causing heat. However, it has little effect on the pathologic evolution of heat causing phlegm.</p>