Conversation so far:
What was the Great Plague?
Outbreaks of plague were not particularly unusual events in London; major epidemics had occurred in 1592, 1603, 1625 and 1636.
What was included in this plague?
Pepys was not among the group of people who were most at risk.
He did not live in cramped housing, he did not routinely mix with the poor.
What happened to the poor?
But, Lord! how sad a sight it is to see the streets empty of people.
Did they become sick?
was shocked by the sight of St Olave's churchyard, where 300 people had been buried.
Around what year was this happening?
June 1665.

Question: What was the cause?
Self-contained rewrite: What was the cause of the Great Plague?