Federico Gambarini/PAP/DPA

The number of deaths in the south-eastern city of Rzeszow caused by an outbreak of Legionella pneumophila has risen to eleven, the State Provincial Sanitary Inspection said on Monday.

The 11, according to the health authorities, were all suffering from other illnesses.

At the same time the number of people in hospital in Rzeszow and neighbouring towns owing to the outbreak rose to 144.

Two people infected with Legionella were also hospitalised in the western city of Ostrow Wielkopolski, while the State Sanitary Inspection also said one person is infected in the eastern province of Lublin and one in the south-eastern region of Malopolska.

On Monday the Health Ministry wrote on X that the “most likely the source of infection is the municipal water supply system, which is confirmed by the first tests results of water samples taken on August 18.”

Adam Sidor, the state provincial sanitary inspector, said at a press conference that four of the nine samples were contaminated with legionella bacteria.

“Two samples were at a high level of more than 2,300 colony-forming units – this is the level where there is a risk of infection just by using the shower,” said Sidor, adding that “one sample was contaminated with bacteria at a medium level and in one colony-forming units were confirmed.”

Just how the bacteria got into the water is still being determined.

Most of the cases concern elderly people who are not very mobile and have not used the city’s infrastructure, have not gone to shopping malls, hypermarkets or been near city fountains.

They also don’t have air conditioning in their houses.

Legionella cannot be contracted from humans or by drinking water containing the bacteria. Infection occurs when somebody inhales drops of water containing the contaminated water.