Sleeping sickness and its kin may have arrived via beehives

AS RECENT EVENTS have made abundantly clear, new viral diseases in people often start as spillovers from infections affecting other species. But viruses are not the only pathogens to do so. Leishmaniasis, sleeping sickness and Chagas’ disease, three potentially lethal illnesses caused by single-celled creatures called trypanosomes, are probably in this category, too. Not only are they spread by insects (sand flies, tsetse flies and kissing bugs respectively), they presumably originated in insects, too (though not necessarily their current vectors)—for most known trypanosomes are insect parasites. That raises the question of how they leapt the species barrier. A study just published in the Proceedings of the Royal Society, by Evan Palmer-Young of America’s Department of Agriculture, suggests the answer may be “bees”.