“When you start reading up on infectious diseases, it isn’t long before you come to the subject of outbreaks, epidemics, and pandemics. The definitions for these terms are less strict than you may think. A good rule of thumb is that an outbreak is when a disease spikes in a local area, an epidemic is when an outbreak spreads more broadly within a country or region, and a pandemic is when an epidemic goes global, affecting more than one continent. And some diseases don’t come and go, but stay consistently in a specific location—those are known as endemic diseases. Malaria, for instance, is endemic to many equatorial regions. If COVID-19 never goes away completely, it’ll be classified as an endemic disease.”