Basel Legionella outbreak ends after cooling system identified

Swiss public broadcaster SRF reported that authorities have declared Basel’s Legionella outbreak over after identifying a cooling system at the headquarters of department store Manor as the source. The outbreak caused one death and 28 illnesses, and no new cases have been recorded since the beginning of August.

One affected person remains in hospital. The patient’s condition is stable and intensive care is not required, Basel’s health department said on Thursday.

Investigations found that a wet cooling system on the roof of the Manor headquarters in Rebgasse was the source of the outbreak. Experts from the cantonal laboratory and University Hospital compared bacterial samples from the system with samples from patients. The bacterial strains matched, scientifically confirming the source of the infections.

Manor said after the outbreak became known that it had shut down the system.

Authorities are still evaluating water samples from the homes of affected patients. So far, they have found no evidence linking shower water in the apartments examined to the outbreak.

Basel’s health authorities warned that Legionella bacteria remain a health risk. The bacteria can occur in shower water and baths and multiply particularly in warm water or when water remains unused for long periods. People become infected by inhaling fine droplets containing Legionella. The disease is not transmitted from person to person.

The canton recommends that households set hot and cold water temperatures correctly, avoid leaving water unused for long periods and thoroughly flush pipes after extended absences. It also plans to advocate for uniform rules across Switzerland on managing Legionella risks.