How dangerous is this swine flue? Probably seversly, in my best guess. 

  It is quite simple math that is at  work. The first cases were seen in early March. If you assume that each victim spreads it to just two more people in about a week, then cases would triple each week (including the original victim each week) . That would work out roughly to the 2,500 now suspected cases in Mexico. Tripling each week would mean about a million and a half cases in three months, rising to 6 billion or so in another eight weeks, i.e. the world's population, roughly. This is less time that it will take to manufacture a vaccine. Even with a widely used vaccine, ordinary flu causes from a quarter to a half million deaths world wide each year. The fatalities from this flu would likely be higher just because of the lack of vaccine, even if it turns out to be no more deadly than normal flus. But the apparently excess deaths in Mexico indicate it might be even more dangerous than that. 

I think that the extreme measures now underway in Mexico - closing schools and many businesses - is entirely justifitied. Any slowing of the spread of the disease would be most welcome, allowing more time to develop a vaccine and to  produce more drugs such as Tamiflu. Otherwise, if the death toll does mount, widespread and extreme hysteria might ensue. This is nothing to take too calmly. On the other hand , the worst thing people can do is mob doctor's offices and ERs. That would only lead to faster spread of the disease. 

I suspect the left should be insisting on a week long shutting down of schools and businesses, and calling on people to stay home. The flu might well die out if that works. Acting as if its nothing would be a terrible mistake.