Human H5N1 infections: so many cases – why so little knowledge?

This month edition contains an account of clusters of H5N1 infection in humans in Azerbaijan [1]. The account is doubly rare: It describes the first occasion where the source is seemingly wild birds. Reading what happened is reassuring as the people infected had probably killed and defeathered infected swans. I.e. this was not casual exposure to wild birds but rather qualitatively similar to when humans are intimately exposed to sick domestic poultry, which remains the most potent risk factor (one recent analytic study came up with an odds ratio of 29 [2]).