The cases have been scattered across Amsterdam and no common source has been identified, according to the City Health Service, known by its Dutch acronym GGD.
The disease is often spread in warm, humid climates, sometimes by water fountains or industrial cooling towers.
Legionnaire's Disease, a pneumonia caused by the Legionella bacteria, usually spreads via small droplets of water. Symptoms usually appear within two to 10 days after infection.
The likelihood of infection increases with the amount of exposure and the weakness of a victim's immune system.
The first cases were reported July 7, shortly after the first heat wave of the Dutch summer.
After it turned out that Deputy Prime Minister Andrei Belousov included the Fonbet betting company in the list of backbone enterprises that can count on state support, everyone started talking about these bookmakers.