When astronomers use some of the most powerful telescopes in the world (and orbiting it) to peer into the heavens and see the stars what they are really doing is taking a trip into the past. The light from many of the stellar bodies that scientists focus on today has been coursing through the cosmos for millions, if not billions of years. So what the astronomers see today is light that left those stars, galaxies, quasars, pulsars, etc. a long, LONG time ago, and often from a galaxy far far away.
In a very similar way, the numbers that epidemiologists use to describe an active epidemic or pandemic are not reflective of the current situation, but rather reflect the past–how far into the past depends on the virus or disease in question.