It showed the man, who appeared to be inebriated and holding a beer can, wearing a medical face mask, which he then removes to stick his fingers in his mouth; he then slowly and purposefully wipes his spit up and down the vertical pole.
The public transport operator STIB confirmed afterwards the entire carriage had to be removed from service and disinfected.
On Wednesday, Belgium's number of coronavirus cases swelled to 314, while the country also recorded its first fatality, when a 90-year-old woman succumbed to the virus.
"Once again we see an increase in the number of new cases," Belgium's FPS Public Health said. "Our hospitals are also seeing more people with lower respiratory tract infections. This may indicate the start of a real epidemic in our country."
Worldwide, the number of cases has passed 115,000, with more than 4,200 recorded deaths.