The claim in the social media post is false.

According to Legionella, a nonprofit organization that shares educational material and scientific research about the disease, Legionnaires’ is not contagious and cannot be transmitted by infected persons or their masks.

“You cannot contract Legionnaires’ disease from wearing face masks. Legionella bacterium is transmitted by aspirating drinking water or breathing in water droplets. Legionella is not spread from person-to-person in respiratory droplets nor does the bacteria survive on dry surfaces. Your mask would not be a source of transmission for the Legionella bacteria,” wrote the organization on its website.

Legionnaires’ disease is a severe form of lung infection caused by breathing in mist or water that is contaminated with the bacterium. The condition is characterized by a cough, fever, headache, and shortness of breath — all symptoms that are also associated with COVID-19 and could potentially result in the misdiagnosis. Though Legionnaires’ is treatable with antibiotics, about 1-in-10 infected people will die.

However, as noted by Legionella, if a person were diagnosed with Legionnaires’ disease, it would not be a consequence of wearing a mask. Water contaminated with the bacteria must be directly inhaled or drank by an individual in order to become infected. As such, a mask would theoretically need to come into direct contact with contaminated water in order for it to be inhaled. Even so, Legionella only grows in standing water under warm temperatures and cannot survive on dry surfaces.