Christian Kabasele joked Watford are "injecting" COVID-19 into players and staff members in a sarcastic response to the club being accused of trying to avoid relegation.
Watford spent much of the Premier League season in the bottom three but sat 17th when the coronavirus pandemic resulted in the suspension of play in England's top flight in March.
Adrian Mariappa confirmed he was one of three people from the Hornets – and six across the Premier League – to test positive for the virus in the first round of analysis conducted by clubs last Sunday and Monday.
Watford captain Troy Deeney has refused to return to training due to health concerns and has voiced his opposition to the season resuming, which is hoped will happen by June 12.
The club also opposed plans to play the remaining Premier League fixtures at neutral venues.
Kabasele hit out at a Twitter user who claimed Watford have been tactically trying to stop 2019-20 reaching its conclusion on the pitch to ensure their top-flight status is retained.
The centre-back posted: "So let me explain our tactic: we are doing one injection of COVID-19 once a week.
"We draw the player/member of staff who gets it [and] like this we are sure that we never play again and avoid relegation."
Kabasele finished the tweet with an emoji of a man facepalming.
When the same Twitter user said Kabasele should "get back to work", he replied: "Can I laugh at someone who can say to someone that he should 'GET BACK TO WORK' when actually he went back to work…
"And it's not a question of being a coward or not when literally you can kill someone from your household if they get the virus from you. Anything else?"
The Premier League announced on Sunday (AEST) that the second round of coronavirus tests returned two positives from as many clubs.