Death toll from legionnaires' outbreak rises to 2 as London-Middlesex Health Unit still seeking source

Investigators with the Middlesex-London Health Unit (MLHU) say they are still struggling to find the source of a local outbreak of legionnaires' disease declared in July that has now led to two deaths. 

There have been a total of 30 confirmed legionella cases between May 1 and Sept. 26, the health unit in southwestern Ontario said Friday. The ages of those infected range from 37 to 76, and more than half are men. All 30 have been hospitalized at some point, with nine admitted to the intensive-care unit (ICU). Four cases remain in hospital.

"It is common in an investigation such as this one that the source of the legionella bacteria that has caused the outbreak cannot be found," said MLHU's acting medical officer of health, Dr. Joanne Kearon. "We conducted our search based on the location of the cases, wind and weather patterns and the types of cooling towers in the region. Unfortunately, while some legionella was identified, none of it linked back to the cases."

The health unit said it has collected environmental samples from 17 cooling tower sites, all close to the geographic centre of the cases in the city's east end. However no samples have yet detected legionella bacteria that are a match for that identified in the cases. 

"It's frustrating," said Kearon. "We all like situations like this to come to a satisfying conclusion. Instead what we can emphasize is the importance of prevention." 

The health unit is asking that all businesses and property managers with cooling towers or other susceptible pieces of equipment ensure they are properly maintained throughout the year. 

Though the source may not be found, the health unit said transmission is slowing and the outbreak may soon be declared over. 

Legionella bacteria are usually found in water environments like hot tubs, cooling towers, large plumbing systems or parts of an air-conditioning system. If misted into the air through wind or fans, people can breathe the bacteria and become unwell. 

The disease is not transmitted from people, or through contaminated foods or public waterworks.

The Canadian government says the average number of reported cases of legionnaires' disease in this country is generally under 100 per year, but the actual number of cases may be much higher as many people with pneumonia may not be tested for legionella.

Symptoms can include cough, shortness of breath, chest pain or discomfort, particularly when breathing or coughing, a high temperature and flu-like symptoms.

The first death from the outbreak was declared in August.