The Black Death was a disease that according to oxford big ideas killed 1/3 of Europe in the medieval era. The disease was a bacterium that could be found in some fleas, which could pass the disease onto humans or animals and kill them.
The impact was death after only roughly 2 days of carrying the disease until later evidence showed that people could be carrying the disease for up to 2 weeks before showing symptoms. Burial grounds were full of people killed by the Black Death. With at least 1/3 of people catching the black death, the disease was quickly spreading all over Europe and with burial grounds being so full people were left on the street to rot until there was somewhere to be buried.
Consequences included severe depopulation this caused shortages in labor and agriculture workers. It had a profound effect on the European history and the history of the world