Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, 60115.
Department of Health Sciences, James Madison University, Harrisonburg, Virginia, 22807.
Evolution. 2020 Oct;74(10):2429-2434. doi: 10.1111/evo.14080. Epub 2020 Aug 25.
The evolution of SARS-CoV-2 remains poorly understood. Theory predicts a group-structured population with selection acting principally at two levels: the pathogen individuals and the group of pathogens within a single host individual. Rapid replication of individual viruses is selected for, but if this replication debilitates the host before transmission occurs, the entire group of viruses in that host may perish. Thus, rapid transmission can favor more pathogenic strains, while slower transmission can favor less pathogenic strains. Available data suggest that SARS-CoV-2 may follow this pattern. Indeed, high population density and other circumstances that favor rapid transmission may also favor more deadly strains. Health care workers, exposed to pathogenic strains of hospitalized patients, may be at greater risk. The low case fatality rate on the Diamond Princess cruise ship may reflect the founder effect-an initial infection with a mild strain. A vaccine made with one strain may confer limited immunity to other strains. Variation among strains may lead to the rapid evolution of resistance to therapeutics. Finally, if less pathogenic strains are largely associated with mild disease, rather than treating all SARS-CoV-2 positive individuals equally, priority could be focused on testing and contact tracing the most seriously symptomatic patients.
SARS-CoV-2 的进化仍不清楚。理论预测，具有群体结构的种群主要在两个层面上受到选择：病原体个体和单个宿主个体中的病原体群体。个体病毒的快速复制被选择，但如果这种复制在传播发生之前使宿主衰弱，那么该宿主中的整个病毒群体可能会死亡。因此，快速传播可以有利于更具致病性的菌株，而较慢的传播可以有利于致病性较低的菌株。现有数据表明，SARS-CoV-2 可能遵循这一模式。事实上，人口密度高和其他有利于快速传播的情况也可能有利于更致命的菌株。接触住院患者的致病性菌株的医护人员可能面临更大的风险。钻石公主号游轮上的低病死率可能反映了创始效应——初始感染一种轻度菌株。用一种菌株制成的疫苗可能对其他菌株提供有限的免疫力。菌株之间的差异可能导致对治疗药物的耐药性迅速进化。最后，如果致病性较低的菌株主要与轻度疾病相关，而不是平等对待所有 SARS-CoV-2 阳性个体，那么重点可以放在对症状最严重的患者进行检测和接触者追踪上。
