Knox E G, Shannon H S
Department of Social Medicine, University of Birmingham, Edgbaston, U.K.
Eur J Epidemiol. 1988 Mar;4(1):83-92. doi: 10.1007/BF00152697.
Squamous cancer of the cervix depends upon infection by Human Papilloma Virus (HPV), of which there are many strains. Some are more dangerous than others and they appear to compete with each other for "territory". The prospective use of vaccines and antiviral agents for HPV infection could disturb the balance of this ecosystem. This study derives the expressions for the prevalences of the different strains at equilibrium. The important parameters of these expressions are 1) the rate of change of sexual partner, 2) infectiousness on contact, and 3) the rates at which an infectious/immune phase decays to a non-infectious/immune phase, and then towards partial or full susceptibility to re-infection. The responses to changes in these parameters are investigated. Analysis shows that the balance between competing strains is locally and precariously stable; it can survive moderate inter-strain variations of the transmission and decay parameters; but larger differences, whether natural or artificially induced, can result in the rapid elimination of the disadvantaged strain. This might be exploited in a preventive programme. Conversely, if a harmless strain were eliminated, the harmful strains would fill the territorial gap, and the incidence of cervical cancer might increase.
宫颈癌的鳞状细胞癌取决于人乳头瘤病毒（HPV）感染，HPV有许多毒株。其中一些比其他毒株更危险，而且它们似乎会相互争夺“领地”。对HPV感染进行疫苗和抗病毒药物的前瞻性使用可能会扰乱这种生态系统的平衡。本研究推导了不同毒株在平衡状态下的流行率表达式。这些表达式的重要参数为：1）性伴侣更换率；2）接触时的传染性；3）感染/免疫阶段衰减至非感染/免疫阶段，然后朝着对再次感染部分或完全易感状态转变的速率。研究了这些参数变化时的响应情况。分析表明，竞争毒株之间的平衡在局部是不稳定且脆弱的；它能够承受传播和衰减参数的适度株间变化；但较大的差异，无论是自然产生的还是人为诱导的，都可能导致弱势毒株迅速被清除。这一点可在预防计划中加以利用。相反，如果一种无害毒株被清除，有害毒株就会填补“领地”空缺，宫颈癌的发病率可能会上升。
