Dowdle W R, Schild G C
Bull Pan Am Health Organ. 1976;10(3):193-5.
Influenza viruses have two surface antigens, the glycoprotein structures hemagglutinin (HA) and neuraminidase (NA). Antibodies to each of these are associated with immunity, but the structures themselves are antigenically variable. When an antigenic change is gradual over time it is referred to as a drift, while a sudden complete or major change in either or both antigens is termed a shift. The mechanism of antigenic drift is usually attributed to selection of preexisting mutants by pressure from increasing immunity in the human population. The mechanism of antigenic shift is less clear, but one tentative hypothesis is that shifts arise from mammalian or avian reservoirs, or through genetic recombination of human and animal influenza strains.
流感病毒有两种表面抗原，即糖蛋白结构血凝素（HA）和神经氨酸酶（NA）。针对这两种抗原的抗体都与免疫力相关，但这些结构本身具有抗原变异性。当抗原变化随时间逐渐发生时，称为抗原漂移，而一种或两种抗原突然发生完全或重大变化则称为抗原转变。抗原漂移的机制通常归因于人群中免疫力增强所产生的压力对预先存在的突变体进行选择。抗原转变的机制尚不清楚，但一种初步假说是，转变源于哺乳动物或禽类宿主，或通过人类和动物流感毒株的基因重组产生。
