One person has died and six others are in hospital due to a legionnaires' outbreak, the Middlesex-London Health Unit (MLHU) said in a news release on Friday. 

Twenty-two cases are attached to the outbreak, and most were found within a five kilometre radius of one another in southeast London. All identified cases have been hospitalized at some point over the course of their illness, the health unit said 

MLHU declared a legionnaires' disease outbreak in London on July 26. It said it first learned it was circulating when employees at a workplace got sick on July 24. The health unit won't disclose the location of the workplace, but says the disease has now spread to a neighbourhood. 

Dr. Joanne Kearon, MLHU's associate medical officer of health told CBC's London Morning on Thursday that most people exposed to the legionella bacteria won't get sick.

On the same day, officials reported that 10 people were hospitalized with the disease.

MLHU is working with Public Health Ontario to investigate the source of the respiratory illness, which causes high fever, chills, a dry cough, shortness of breath and can lead to pneumonia. Its symptoms usually present within two to 10 days after encountering the bacteria, MLHU said. 

"We are currently sampling cooling towers and units that are in the area that we suspect the source is," Kearon said. 

"These investigations with legionella are difficult, they are complicated. They tend to last some time because we may actually find sources of legionella that aren't related to this outbreak."

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

The disease is not transmitted from people, or through contaminated foods or public waterworks. It can take weeks to identify the source and confirm it as the outbreak's cause, MLHU said, adding that sometimes the source is never definitively found but the outbreak ends naturally. 

MLHU is warning business owners and property managers to ensure all cooling equipment is regularly maintained and sanitized to reduce risk of further legionella outbreaks. 

Legionnaires' Disease: A Rare but Potentially Deadly Illness

Legionnaires' disease is a severe form of pneumonia caused by the Legionella bacteria. The bacteria is commonly found in water sources, and it can be spread when the bacteria is aerosolized, meaning it becomes airborne and is inhaled. This can occur in places like cooling towers, hot tubs, and even showerheads.

Most people who are exposed to Legionella bacteria don't get sick. However, those who do can experience severe symptoms, including fever, chills, coughing, and difficulty breathing. In some cases, Legionnaires' disease can be fatal, especially for older adults, people with weakened immune systems, and those with underlying health conditions.

London Outbreak: Investigation and Prevention

The Middlesex-London Health Unit is investigating the source of the outbreak and is working to prevent further cases. Public health officials are urging residents to take precautions to reduce their risk of exposure, such as regularly cleaning and maintaining cooling towers and other water systems.

The Importance of Public Health Measures

Outbreaks like the one in London highlight the importance of public health measures in protecting communities from disease. Public health officials play a crucial role in investigating outbreaks, identifying the source of infection, and implementing measures to prevent further spread. In addition, public health campaigns can educate the public about the risks of disease and how to protect themselves. This includes promoting good hygiene practices, staying up-to-date on vaccinations, and seeking medical attention when necessary.

Conclusion: The Importance of Being Vigilant

The London Legionnaires' outbreak is a reminder that infectious diseases can pose a significant threat to public health. It is important to be vigilant about protecting ourselves and our communities from these threats. This includes staying informed about outbreaks and taking steps to reduce our risk of exposure. By working together, we can help to prevent the spread of disease and keep our communities safe.