Abstract：
The time-honored paradigm in the theory of virulence evolution assumes a positive relation between infectivity and harmfulness. However, the etiology of respiratory diseases yields a negative relation, with diseases of the lower respiratory tract being less infective and more harmful. We explore the evolutionary consequences in a simple model incorporating cross-immunity between disease strains that diminishes with their distance in the respiratory tract, assuming that docking rate follows the match between the local mix of cell surface types and the pathogen\'s surface and cross-immunity the similarity of the pathogens\' surfaces. The assumed relation between fitness components causes virulent strains infecting the lower airways to evolve to milder more transmissible variants. Limited cross-immunity, generally, causes a readiness to diversify that increases with host population density. In respiratory diseases that diversity will be highest in the upper respiratory tract. More tentatively, emerging respiratory diseases are likely to start low and virulent, to evolve up, and become milder. Our results extend to a panoply of realistic generalizations of the disease\'s ecology to including additional epitope axes. These extensions allow us to apply our results quantitatively to elucidate the differences in diversification between rhino- and coronavirus caused common colds.
摘要：
毒力进化理论中历史悠久的范式假定传染性和危害性之间存在正相关关系。然而,呼吸系统疾病的病因产生了负相关，下呼吸道疾病的感染性较低，危害更大。我们在一个简单的模型中探索进化结果，该模型包含疾病菌株之间的交叉免疫，这些疾病菌株随着它们在呼吸道中的距离而减少，假设对接速率遵循细胞表面类型的局部混合与病原体表面之间的匹配，和交叉免疫病原体表面的相似性。健身成分之间的假定关系导致感染下气道的毒株进化到更温和，更多可传播的变体。有限的交叉免疫通常会导致多样化的准备，这随着宿主人口密度的增加而增加。在呼吸系统疾病中，上呼吸道的多样性最高。试探性地,新出现的呼吸系统疾病可能开始低毒，进化并变得更温和。我们的结果扩展到疾病生态学的现实概括，并包括其他表位轴。这些扩展使我们能够定量地应用我们的结果来阐明鼻和冠状病毒引起的普通感冒之间的多样化差异。
