The typical hospital houses large numbers of people in close confines, many with compromised immune systems and all reliant on the same water supply infrastructure.

Over time, microbes build up in the plumbing system of such an environment, and vulnerable patients are exposed to bacteria strains that would not harm a healthy person but can prove deadly to those with weakened immunity.

Between 2004 and 2005, six premature infants died in a neo-natal ward at Centre Hospitalier Universitaire (CHU) Sainte Justine in Montreal, Canada.

Following the first death, the hospital conducted an investigation and was unable to find the infection source. The ward, which had been overcrowded, was disinfected and remained open. Additional deaths over an 18-month period triggered the closure of the ward, and a subsequent investigation identified festering, blocked sinks and a corroded plumbing system as the source of a bacterial colony of pseudomonas aeruginosa.

It was reported by Radio Canada that 50 patients had been exposed to infection, including the six infants, and that they had contracted it from water carrying the bacterium.

Pseudomonas aeruginosa, a waterborne pathogen, thrives in harsh conditions and attacks the respiratory system, causing pneumonia and septicaemia in immuno-compromised patients. The bacterium commonly exists in the environment and does not pose a risk to healthy people. However, there is a mortality rate of up to 40% when it is transferred to newborns, the elderly and patients with immune systems weakened by illness or operation – and an incalculable cost to a hospital’s reputation.

University of Pittsburgh special pathogens laboratory director Dr Janet E. Stout says patients in transplant units, haematology, oncology, burns, neo-natal intensive care and other intensive care units are at greatest risk of waterborne infections and need very high quality water.

The US-based Committee to Reduce Infection Deaths (RID) estimates that 100,000 people will die this year from infections acquired in hospital. Patients come into contact with waterborne bacteria, or pathogens, not only through ingestion, but also bathing, ice cubes for mouth sores, inhalation of shower mist or being treated with instruments washed in hospital water.

Dr Stout, an international expert on waterborne pathogens, notes that no single systemic disinfection technology can completely eliminate these micro-organisms from hospital plumbing systems. Many of the microbes live in biofilms – communities of micro-organisms that adhere to the pipes and are resistant to systemic disinfection treatments.

“We are interested in waterborne pathogens for two reasons – because they can cause infections, particularly in immuno-compromised patients, and because they are increasingly becoming resistant to antibiotics,” she says.

“About 50% of the plumbing systems of large buildings – hospitals, hotels, offices – are colonized with bacteria such as legionella and pseudomonas aeruginosa. We need to reduce point-of-source exposure to prevent these bacteria colonizing people, in order to reduce the risk of creating drug-resistant bacteria through the over-use of antibiotic treatment.”

In other words, prevention is the key.

Dr Stout believes the most effective way of protecting hospital patients is point-of-use filtration.

“The efficacy of point-of-use filtration in preventing against micro-organisms was demonstrated in a 2005 study.