In order to understand how bee colonies die in the winter it is not only important to know which bacteria and viruses are present, it is also necessary to understand how these become present in large numbers in such a short space of time. The answer to the question as to what all these microorganisms do is also essential. In other words, which mechanism do they use in the competition with other microorganisms. To help us understand this process, we can make use of the concept of dominance.
Dominance occurs in a situation where a single organism has gained the upper hand. This happens, for example, when the conditions for that organism are extremely favorable, or when the competition disappears due to other organisms. Dominance can also occur at bacteriological and viral level. Such a situation where just one or a few dominant species are present can quickly transform into a fatal situation.
Examples have been described for bees where bacterial infections felled whole colonies in 2 to 3 days. Surprisingly enough, this was not due to ‘recognized pathogens’, but to certain common types of bacteria present in bees' intestines which suddenly became dominant. From a virology perspective it is thought that these kinds of events are caused by viruses, for instance by injecting healthy bees with these pathogens. Because scientists do not know exactly how these viruses work, it is possible that this conclusion is incorrect.