California businesses are reopening after the long lockdown. But our empty offices, hotels, restaurants, and gyms may have collected more than just dust; a deadly bacteria called legionella could be growing in the pipes.

Legionella pneumophila is one of over 58 strains of Legionella bacteria that flourish in showers, sinks, cooling towers, hot tubs, decorative water features, hot water tanks, and plumbing systems. When aerosolized droplets of Legionella pneumophila are inhaled, the bacteria causes a deadly form of pneumonia known as Legionnaires' Disease. Although Legionnaires’ Disease is treatable with antibiotics, about 1 out of 10 people die from the illness; the elderly, smokers, and the immunocompromised are especially vulnerable. The CDC reported about 10,000 cases of Legionnaires’ Disease in 2018, but experts believe the true number of cases is higher. Case numbers are also on the rise; the rate of reported cases grew ninefold from 2000 to 2018. Health officials remain unsure if the trend is an artifact of better testing or indicative of environmental and demographic factors like antiquated infrastructure and a larger elderly population. If the trend continues, the US may be on track for a historic number of cases in 2021; experts fear…