Swine flu is killing young people rather than the very elderly, and although winter is just starting, more young people have already died of flu than normally die over the entire winter.
Nearly 5000 people worldwide are known to have died of swine flu so far. But on average 36,000 are said to die of flu each winter in the US alone. On the basis of such numbers, many have concluded – wrongly – that swine flu is less dangerous than normal flu.
These numbers should not be compared directly. The 36,000 figure comes from epidemiological studies. Because the timing of flu outbreaks varies from year to year, the normal number of deaths in any month can be compared with the number of deaths in the same month when there was a flu outbreak, says Lone Simonsen of George Washington University in Washington DC. Such studies reveal a bulge in deaths during and just after the flu season every year, mainly among the elderly. Many are clearly due to flu and other lung infections that can follow it, but more than half are not obviously connected, because flu often kills in indirect ways, by triggering heart attacks or strokes, for instance.
By contrast, the deaths attributed to swine flu are those directly caused by respiratory infection with the pandemic virus. Indirect deaths – the majority of the 36,000 figure for regular flu – are not being counted. The full death toll for 2009 H1N1 flu will not be known for a while, if ever. Perhaps there will be fewer deaths than normal because older people, more at risk from secondary events such as heart attacks, have some immunity to the virus. However, the total seems likely to be higher simply because the virus will infect far more people than normal, and it kills directly more often.
The impact of a pandemic is not simply about the number of deaths, though. This pandemic, like previous ones, is killing mainly young people, not the very elderly as flu normally does (see diagram). By early October, 76 children and adolescents in the US had already died of swine flu (see diagram). That is more than the usual winter toll, and the winter has just begun.
Read more: Swine flu: Eight myths that could endanger your life