2.2.2. Active surveillance
Active surveillance schemes fill many of the gaps of passive surveillance. These are usually statistically designed sampling schemes to determine pathogen prevalence within the general bee population, irrespective of symptoms. The bee samples are alive when collected, making molecular detection uniform and reliable, and the data are an accurate representation of the complete pathogen presence within a region. Often samples are taken repeatedly from the same colonies throughout a season, which has to be taken into account during data analysis. A sub-category of active surveillance systems is ‘sentinel’ surveillance, i.e. a series of designated ‘monitoring’ colonies placed to catch certain pathogens before they reach a particular region.