The summer of 1976 was projected to be a busy one for Philadelphia, as the city was hosting celebrations for the bicentennial anniversary of the signing of the Declaration of Independence.

But that season was cut short due to a mysterious illness that infected guests at the Bellevue-Stratford Hotel on Broad Street and ultimately killed 34 people. Many tourists, not knowing the name nor source of the disease, avoided visiting.

“There really weren’t a lot of lines with the Liberty Bell,” said epidemiologist Dr. Robert Sharrar, who was chief of the communicable disease control program at the Philadelphia Department of Public Health at the time.

The illness was Legionnaires’ disease, an illness caused by a bacteria that lives in water systems. It is not contagious and takes the form of a serious form of pneumonia. Legionella pneumophila — the bacteria that causes the disease when people breathe it in through mist or vapor — grows in warm, stagnant water and often is found in shower heads, faucets, pipes, cooling tanks, ice machines and other manmade water systems. It’s one of the deadliest waterborne diseases in the U.S. but is preventable.

Fifty years after the Bellevue-Stratford outbreak, Pennsylvania lawmakers are considering legislation that aims to reduce the risk of Legionnaires’ disease infections. HB 2085, proposed by Ismail Smith-Wade-El (D-Lancaster), would implement new requirements for public water systems and building owners, similar to a 2024 New Jersey law. On July 20, the state House Consumer Protection, Technology and Utilities Committee held a public hearing for the bill at Philadelphia City Hall.

“Pennsylvania has a unique place in the history of this disease. It should also have a leadership role in preventing it,” said Bill McQuade, an engineer and former president of the American Society of Heating, Refrigeration, and Air Conditioning Engineers, who expressed his support for the bill.

Smith-Wade-El told the Local he proposed the bill due to the prevalence of Legionnaires’ disease and a case that occurred at Lancaster County Prison in 2023.

“Being a legislator is about finding the next way we can protect the most vulnerable people in our communities, and this is one that is impacting my community in Lancaster,” he said. “We wanted to wade into it in a serious way, and we’re open to any conversation that’s going to help us do so.”

Legionnaires’ disease cases have been increasing in the U.S., with a peak in 2018, according to the U.S. Centers for Disease Control and Prevention. A recent outbreak in New York City has resulted in the deaths of five people, as of Monday. City officials say the source of exposure has been remedied.

As many as 18,000 people in the U.S. are hospitalized every year for Legionnaires’ disease, but cases are under-reported, according to the CDC. There’s a 10% fatality rate and those at risk of contracting it are middle-aged or older people, males, smokers, those with weakened immune systems and residents of aging and poorly maintained buildings. It’s primarily treated with antibiotics.

Pennsylvania’s infection rate is nearly double the national average, Kristina Zwolenik, a waterborne epidemiology research associate with the state Department of Health, said at the hearing. The state recorded 1,231 confirmed or probable Legionnaires’ disease cases between 2021-23. State officials reported as many as 450 cases in 2025. Zwolenik said the cause of most of the outbreaks was poor building maintenance.

“We routinely trace cases back to poor, irregular or non-existent maintenance of hot tubs, ice machines and cooling towers as well as building renovations that leave water stagnant in unused spaces,” she said.

HB 2085 requires the Department of Environmental Protection and Department of Health to come up with regulations to reduce the development of Legionella bacteria. Facility and building owners must implement a water management program two years after the bill takes effect.

Charles N. Haas, an environmental engineering professor at Drexel University, said prevention of the disease is a shared responsibility between water utilities and property owners. He urged the committee to sharpen the water management portion of the bill.

“I think what the bill gets right is the requirement for high-risk facilities to have a water management plan. That’s where the science says the fight belongs,” Haas said.

But representatives of water utilities in Pennsylvania said Legionella is a problem for property owners and the proposed requirements would increase utilities’ operational costs due to additional infrastructure and staffing, leading to higher bills for ratepayers. Zwolenik said the health department would have to hire more staff under the legislation.

Charlotte Katzenmoyer, the chief executive officer of Harrisburg-based Capital Region Water, said increased chlorine levels could create disinfection byproducts associated with health risks and carcinogens.

Ben Jewell, commissioner of the Philadelphia Water Department, said the utility would need to add staff members and at least three chlorine booster stations to comply with the bill, and the expenses would lead to increased rates for Philadelphians.

“The requirements for public water systems proposed in House Bill 2085 may result in harmful water quality side effects, while not effectively providing risk reduction for Legionella,” he said.

Smith-Wade-El told the Local that the next steps are to work with scientists, water utilities, the Department of Environmental Protection, legal experts and other stakeholders to create an updated version of the bill. The full chambers of the House and Senate aren’t set to convene until September.

Philadelphia’s place in history

The Mütter Museum of the College of Physicians of Philadelphia recently opened an exhibit dedicated to the 50th anniversary of the 1976 outbreak. The exhibit proposes that, like COVID-19, new public health threats are emerging that can cause significant ripples in the economy and political sphere.

From July 21-24, 1976, more than 4,000 members of the Pennsylvania chapter of the American Legion — America’s largest veterans’ service organization — and their families gathered at the Bellevue-Stratford for the 58th annual convention. Within days after the event, attendees were hospitalized with a severe atypical pneumonia. By late August, 34 people had died and 221 were sick. They were veterans of the Korean and First and Second World Wars. Some were people who had walked near the hotel, not inside, during those few days.

The mysterious outbreak made headlines worldwide and led to the largest investigation in the CDC’s history. The only clue was the proximity to the hotel. The CDC realized early on that it was not a citywide problem, Sharrar said, as it wasn’t contagious.

“Broad and Lombard, which is where my office was, has an auditorium, and they turned that auditorium into a command center,” Sharrar, a fellow at the College of Physicians of Philadelphia, said. “We probably had 50 to 100 people in there collecting data, analyzing data, entering it into the computer system, and analyzing it. It caused quite a turmoil throughout the city.”

The media gave it the name Legionnaires’ disease, as well as the Philly Killer. There were multiple conspiracy theories about the outbreak’s cause: experiments by the CIA, aliens and Soviet espionage to name a few. The Bellevue-Stratford closed in November 1976.

In January 1977, microbiologist Dr. Joseph McDade finally discovered a long, rod-shaped bacteria that he and his team named Legionella pneumophila. The bacteria was hidden along the sides of Bellevue’s air conditioning through the cooling tower.

“It was very comforting because you kind of felt you were missing something,” Sharrar said.

How to regulate it

Pennsylvania Department of Health officials investigate every reported case of Legionnaires’ disease, a spokesperson for the department said. If a building is the suspected source, its management puts temporary public health protections in place until officials complete tests and cleanups. In Philadelphia, the water department uses chlorine to control bacterial growth, a spokesperson for PWD told the Local. It’s used this process since the late 1960s and ’70s.

Environmental microbiologist Dr. Jennifer Clancy of J. Clancy & Associates, LLC, has 46 years of experience in working with Legionnaires’ cases. She said the reason that cases have risen could be partly due to advanced surveillance and increasing awareness.

Clancy and most of the experts who testified at City Hall agreed that there needs to be more regulation to prevent Legionnaires’ disease infections. She said lawmakers shouldn’t regulate drinking water and instead should focus on water fixtures in buildings.

“That’s where it grows. That’s where the control really needs to be,” she said.

Steve Chintaman, the vice president of government affairs with the Pennsylvania Apartment Association, said the requirements for sampling and planning could increase operational costs for property management companies, especially affordable-housing developments.

Smith-Wade-El said he’s hoping water utilities and the Department of Environmental Protection can assist property owners is developing affordable management plans. He plans to work with property managers to ensure the bill doesn’t significantly raise costs for tenants.

Clancy said there should be more water management regulations, but it’s difficult to enforce them. She said the solution should involve an educational component. She provides workshops to clients and encourages utilities to educate their customers.

The risk of Legionnaires’ disease could be increasing due to climate change, as heat waves become more intense and frequent, resulting in more use of air conditioning.

“It’s good to see that legislators are trying to move this ahead and trying to figure out ways to control this,” she said, “because we know it’s controllable.”

Abby Weiss is an environmental reporter for the Local and a Report for America corps member. She can be reached at abby@chestnuthilllocal.com.