Metselaar D
Lancet. 1976 Jan 24;1(7952):174-6. doi: 10.1016/s0140-6736(76)91276-9.
In Kenya for more than twenty years a remarkable periodicity has been observed in the circulation of type-1 poliovirus and in epidemics of poliomyelitis caused by this virus type. Periodicity was less obvious for poliovirus types 2 and 3. Cases of poliomyelitis increased, and this trend was only partly controlled by vaccination. It is postulated that virulent strains of poliovirus became dominant because of selection pressure. It is suggested that this selection pressure occurred earlier in economically developed countries and was partly responsible for the pronounced changes in the epidemiology of poliomyelitis seen in such countries.
在肯尼亚，二十多年来一直观察到1型脊髓灰质炎病毒的传播以及由该病毒型引起的脊髓灰质炎流行存在显著的周期性。2型和3型脊髓灰质炎病毒的周期性则不太明显。脊髓灰质炎病例有所增加，而这种趋势仅通过疫苗接种得到了部分控制。据推测，由于选择压力，脊髓灰质炎病毒的强毒株成为了优势毒株。有人认为，这种选择压力在经济发达国家出现得更早，并且部分导致了这些国家脊髓灰质炎流行病学的显著变化。
