Is the new H1N1 influenza virus actually in fact more virulent than seasonal flu?
Greenberg: The answer to that isn’t totally clear as yet. Above and beyond the level of pre-existing immunity people have to them, some influenza strains can be more virulent than others. We know something, but not a lot, about what determines these differences in virulence between strains. In the case of the famous Spanish 1918 pandemic flu, not only was the entire world susceptible to it, but it caused a disease that, first, made you incredibly sick. And, second, it frequently made young, healthy people sick. Normally influenza, while nasty enough in itself, is mainly catastrophic only for very young babies and the elderly. The indications so far are that this new strain is not inordinately virulent. It’s probably more or less similar to a normal influenza, except that nobody has any immunity to it. So you’ll have more people sick – and therefore more people very sick, because a certain percentage of people who get influenza get very sick. Every year in the United States alone, about
