There is some evidence to suggest that previous exposure to HSV1 and development of antibodies will result in less severe reaction/illness in those later infected with HSV2. (However, it will not provide immunity). This may help to explain why such a large proportion of those infected with HSV2 (upwards of 80%) of the 25-30% of people who eventually will contract it, are either unaware of their infection or have had symptoms so mild they have mistaken them for something else.