Leslie Young tweeted the photo outside a hospital after anti-lockdown activists shared fake footage to claim hospitals are deserted.
The West Midlands pre-hospital nurse said: "So for those who believe the false social media posts about empty wards in hospitals, who do you think this lot are dropping off?"
His area's hospitals are "fully stretched" at one of the highest alert levels of CRITCON level three, the Sun reports.
Leslie added: "Looked at the faces of some of my colleagues today & they have lost their spark.
"They’re tired, stressed and breaking, yet they are out on the COVID frontline working hard.
"This pandemic is taking its toll on us. Help us by being kind and following the rules."
NHS England chief Sir Simon Stevens has said: "When people say that coronavirus is a hoax, it is a lie.
"If you sneak into a hospital at 9pm and film an empty corridor and then stick it on social media claiming it 'proves hospitals are empty', you are responsible for changing behaviour that will kill people."
One Facebook group sharing pictures and videos of 'empty' hospitals has more than 13,000 members, the BBC reports.
Its administrators are apparently linked to another Facebook group peddling the 'Great Reset' conspiracy about the pandemic.
Hospitals have had to separate Covid patients and cancel non-urgent care to free up capacity.
This may leave some areas appearing empty while frontline staff deal with a surge in patients.