Another person dead in London, Ont., legionnaires' outbreak

Another person has died and 20 more are sick from legionnaires' disease in London, Ont., public health officials warn. 

That brings the outbreak to a total of two people dead and 64 sick since it was declared by the Middlesex-London Health Unit less than a week ago, on July 8. 

The patients have ranged in age from 23- to 93-years old, but health officials still don't have an exact source of the deadly bacteria, or whether it is linked to an outbreak that killed two people last year. 

On Monday, officials released a map to indicate the general area most impacted by the outbreak, though it takes in a large chunk of the city. 

"Despite this cluster of cases, the overall risk to the broader community remains low, particularly for individuals who are not at higher risk," officials said.

"Homes and businesses in the area remain open and are expected to follow all recommended health and maintenance protocols. Residents are not discouraged from continuing their daily routines in this area."

The blue circle of the map represents a six-kilometre radius around the average location of all home addresses of reported cases, and is a snapshot in time, health officials say. 

"The 6-kilometre radius may not reflect the actual distribution or movement patterns of individuals affected by the outbreak," the health unit said in an emailed statement. 

"Although this map shows where the greatest density of cases reside, there are confirmed Legionnaires' cases outside of this area." 

Legionnaires' disease is caused by legionella bacteria, naturally found in water sources such as hot tubs, cooling towers, hot water tanks, large plumbing systems or parts of air-conditioning systems. 

Legionella is not transmitted from person to person. If the bacteria are aerosolized or misted into the air (via wind or fans), people may inhale the bacteria and become unwell. Most people exposed to legionella don't get ill, but some may experience Pontiac fever, a mild, flu-like illness that commonly resolves itself.

Individuals who are older, have lung problems or are immunocompromised are at greater risk of serious infection.

Health officials defended taking so long to release a map of the area, saying it took time to gather sufficient information to get a map together and that the priority was working with property owners and operators of water-cooling systems to clean and maintain their systems as a precautionary measure. 

"Legionella aerosolizes and travels significant distance. The source of the Legionella spread has not yet been found," officials said.