Today, the CDC reports 403 confirmed cases of H1N1 (the flu formerly known as “swine”) in the US, and the WHO reports a total of 1124 cases in 21 countries. There have been 25 deaths in Mexico and two in the US.

The increase in numbers is largely due to cases that had already been reported as probable finally being laboratory confirmed. Here in the DC area, we’re hearing less news about additional probable cases, and several school districts that had announced closures have now reversed themselves, as the CDC changed its stance from advising school closures when a flu case was reported to urging parents to keep sick children at home. Mexico is allowing businesses, schools, and other public venues to reopen this week.

The news is better than many of us feared it would be — but that doesn’t mean that governments and the WHO overreacted. If not for the dramatic measures that Mexico and other governments imposed, our situation right now would probably be worse. How much worse? Maybe only a little worse (a few hundred more people feeling miserable for a week, a few dozen more hospital emergency rooms overstretched), but possibly a whole lot worse. The flu virus that’s circulating in the US right now appears to cause relatively mild illness, but if it circulated through a wider population over a longer time period, it would mutate further and could become far more virulent.

DemFromCT at Daily Kos has an excellent post up that illustrates the need to take decisive action that might seem like an overreaction in the public’s eyes. I urge everyone to read the whole thing, but I particularly want to highlight his comparison of two curves. There’s the sharp curve of the pandemic outbreak with no intervention, which results in a high peak and a lot of cases. With intervention, the slope of the curve is reduced, and so the overall number of cases is far lower. The problem is that if you wait until the severity of the outbreak is evident – for instance, unitl schools are reporting dozens of flu cases rather than one or two – you’re already well along the sharp slope of the curve, and it’s too late for intervention strategies to work well.

It’s also important to remember that while the interventions have helped, we may not be out of the woods yet. The virus could still spread widely throughout the Southern Hemisphere, where flu season is just beginning.  It could also hit the Northern Hemisphere harder when our next flu season begins. Keep washing your hands, covering your cough, and limiting your contact with others as much as possible if you get sick.