The Minnesota Department of Health thinks it knows how Legionnaires' disease has spread to nearly two dozen people in the Twin Cities suburb of Hopkins: Cooling towers.
The department said Friday it's confirmed 23 cases to date of the respiratory disease, which is spread through water droplets, the CDC says. That's three more cases than what had been confirmed earlier this week.
An elderly patient who contracted Legionnaires' died last week, but it's not clear whether Legionnaires' actually caused the death.
The department has been investigating the source of the outbreak since it was first reported last month, and could find no common link between any of the patients except they all live, work, or had spent time in Hopkins.
Is it cooling towers?
But in Friday's update, they said the most likely cause is contaminated water that was turned into mist by a cooling tower – air conditioning units for larger buildings.
They can't get more specific than that right now. At this point, they've found seven spots with one or more cooling towers as possible sources (and will continue looking for more). Those have either been treated, or are in the process of being treated, by the owners.
Officials have also taken environmental samples from nearby, and they're being tested. But Legionella (the bacteria that causes Legionnaires' disease) grows very slowly, so results can take awhile.
The department also brings up an interesting point: There's no Minnesota law that regulates cooling towers, so there isn't a master list of all cooling towers in a city or county. It's also up to each cooling tower owner to make sure the units are up to industry standards.
More about Legionnaires'
Legionnaires’ disease is a type of pneumonia characterized by fever, chills, headaches, muscle aches, fatigue, shortness of breath, cough, mental confusion, diarrhea, and vomiting, the Health Department says.
It can be treated with antibiotics. The CDC says about 1 in 10 patients with Legionnaires’ disease will die from complications of the illness.
Those at greater risk of getting sick with the disease include people older than 50, smokers, people with lung disease, and those with weakened immune systems.
The Minnesota Department of Health says the number of cases has risen. From 2012-2015, they recorded anywhere from 50-58 confirmed cases. In 2016, they've already recorded more than 90.