Despite their name, their sting is no more venomous than that of the common honey bee, but they are far more aggressive in defence of their hives. Killer bees can mount massed attacks which can inflict hundred of stings simultaneously and will pursue intruders (people and livestock) for up to a kilometre. They also have the proven ability to subvert domesticated honey-bee colonies.
Despite incomplete reporting, deaths from bee stings in Brazil, for example, are between 300 to 400 per year, as compared to 100 in the USA, towards which the bee population is spreading. The problem originated in Brazil, where queens were imported from South Africa in 1956 on the theory that the bee families they generated would be more productive in tropical climates that those of the European species. In 1957, 26 African swarms escaped. The Africanized bee reproduces faster than European varieties, and the worker bees fly longer distances in search of nectar. After only a few years they were flourishing, with up to 100 swarms per square kilometre. From the Brazilian interior, the bees spread southward into Paraguay and Argentina and thousands of miles across the Amazon basin. By 1979, they were in Venezuela and Colombia. They are well established in Costa Rica, where they arrived from Panama in 1982. Swarms are advancing up the Atlantic and Pacific sides of the Central American isthmus at up to 400 miles (650 kilometres) a year and are heading toward Mexico and the USA.
This spreading of the African bee has had catastrophic effects on commercial beekeeping. In Venezuela, production has dropped 80%. If the Africanized honey bee spreads to all 11 States in the USA that have 240 frost-free days a year, direct damage to the beekeeping industry could be more than $50 million a year. The new bee threatens annual sales of $150 million in honey, wax, pollen and other products.