Thank you to Jaime E. Garza, Apiary/Agricultural Standards Inspector, Department of Agriculture, Weights & Measures, County of San Diego for the following:
"To help improve the overall health of our honey bee community it is important for beekeepers to familiarize themselves with healthy brood conditions and types of brood diseases.
I have attached a helpful resource on American Foulbrood Disease which is a highly contagious bacteria with no cure. The disease weakens and in most cases kills a bee colony. During times of dearth a weakened infected bee colony may be susceptible to robbing by other honey bees from other colonies which can cause the bacteria to be spread. The disease can be spread by bees, honey, propolis, hive tools, frames and other beekeeping equipment."