August 2018 broad core update (Medic)
Large core update that disproportionately affected health, medical and other your-money-or-your-life sites, nicknamed Medic.
What changed
Google confirmed a broad core update on 1 August 2018 that produced unusually large swings, concentrated in health, medical, finance and other consequential topics. Because of that concentration the industry named it Medic and linked it to the expertise, authoritativeness and trustworthiness concepts in Google's Search Quality Rater Guidelines. Google itself said there was no fix, that the update was not aimed at any single sector, and that publishers should read the rater guidelines to understand what raters are asked to assess.
Timing
Rollout began 1 August 2018. No completion date was announced. Rankings typically remain unstable for the whole rollout window, so measurements taken inside it are not a reliable read on the outcome.