Umpires took the decision after several members of the hosts' squad were identified as close contacts following just one day of play at the County Ground
Derbyshire and Essex's LV=Insurance County Championship clash has been abandoned after a positive Covid-19 case in the hosts' camp.
Several teammates of the unnamed player have been identified as close contacts and have also gone into self-isolation.
Due to the impact on Derbyshire, who are already without nine players due to injury, umpires James Middlebrook and Neil Mallender have taken the decision to abandon the game at the County Ground.
A statement added: "The ECB has worked closely with Public Health England and both Derbyshire and Essex County Cricket Clubs with the health and safety of players, staff and officials the first priority."
Points from the match will be confirmed in due course. Essex had already won three bonus points after dismissing the home side for 146 on day one. They eventually closed on 86 for 3.
However, with the Chelmsford club needing a win to stand any chance of progressing to the championship group it likely ends their title reign and spell as holders of the Bob Willis Trophy.
The episode is the latest instance of Covid causing chaos across English cricket.
Last week, England's one-day international squad were all forced to self-isolate after an outbreak of seven positive cases. An entirely new group was called up for the Pakistan series.
Over the weekend it was confirmed that the Kent squad that played Surrey was in the T20 Blast were also self-isolating after a single case emerged, which impacted on selection for the Championship game with Sussex.