Three people have died and dozens have become infected after being diagnosed with legionnaires' disease during an outbreak in Milan.

Health officials are scrambling to contain the spread, which they fear has contaminated the local water supply.

Legionnaires' disease is a potentially fatal form of pneumonia and everyone is susceptible to infection. The risk increases with age but some people are at higher risk including people over 45.

Around 90 percent of people exposed to legionella bacteria, which can grow and spread in built water systems like cooling towers and pools, do not experience symptoms.

But up to 15 per cent of those who do become ill can suffer from severe disease, which can lead to life-threatening pneumonia.

The latest figures from the European Center of Disease Prevention and Control (ECDC) show at least 49 cases of the disease have been recorded in the Lombardy region.