 Quarantining (isolation) of ships had been used during previous outbreaks and was again introduced for ships coming to London in November 1663, following outbreaks in Amsterdam and Hamburg.Two naval ships were assigned to intercept any vessels entering the Thames estuary.Ships from infected ports were required to moor at Hole Haven on Canvey Island for a "trentine" – period of 30 days – before being allowed to travel up-river.