The force said a 27-year-old man was arrested over alleged calls online for centres to be bombed and staff to be attacked.
Two men, aged 21 and 28, were arrested in separate cases on suspicion of using social media to encourage people to deliberately spread the coronavirus.
Officers said the 28-year-old was also suspected of putting other people at risk during restaurant visits while he was allegedly infected with the virus.
“It’s obvious that he was deliberately leaving some tissues on the table and on the utensils,” claimed superintendent Wilson Tam from the force’s cyber security and technology crime bureau.
Tam added that the man was expected to appear before Kowloon City Magistracy later on Wednesday.