Student or Learner
What does "epidemic threshold" mean ?
It's something as where the epidemic begins, or it's something about the level of the disease.
context: "...and Congo, where the epidemic threshold has been reached.."
This is the meaning I have found: An increase in deaths of 1.645 standard deviations above the seasonal baseline (5% of all) is defined as the "epidemic threshold" ie it is a statistical measurement derived from figures for the disease concerned.
Here's another explanation (this time citing influenza):
The CDC's definition of a flu epidemic relates to the percentage of deaths in a given week caused by influenza and pneumonia. The "epidemic threshold" is a certain percentage above what is considered normal for that period. The normal level, or baseline, is statistically determined based on data from past flu seasons.