Antonine Plague
The plague broke out in 165 AD and lasted to 180 AD sweeping across the Roman empire. Coincidently these dates are when the Antonine wall was abandoned and then secondly when the Scottish swarmed over Hadrian’s wall. It is said to have been smallpox and killed about 10% of the population. There are few records so it is unclear as to whether it arrived in Britain.
By Unknown author – Public Domain, https://commons.wikimedia.org/w/index.php?curid=6573697
References
- Galen and the Antonine Plague R. J. Littman, M. L. Littman The American Journal of Philology, Vol. 94, No. 3 (Autumn, 1973), pp. 243-255
- https://en.wikipedia.org/wiki/Antonine_Plague?wprov=sfla1