The Dose22:32Why do I need to know about Legionnaires’ disease?
When Dr. David Fraser was tapped to be the lead field investigator for a strange respiratory outbreak in Philadelphia in 1976, he suspected something larger was at play.
“We knew at that time there were 11 deaths, so I knew it was more than a couple pneumonia cases,” he said.
The outbreak was connected to an American Legion National Convention held between July 21 and July 27 at the Bellevue-Stratford Hotel in Philadelphia.
The first patient died a few days after the convention ended, and more fatalities followed. Fraser and other experts say the 1976 legionnaires’ disease investigation revealed how modernization, through things like HVAC systems, can unintentionally increase the possibility of exposure to environmental pathogens — and how critical it is to widely share public health updates.
“Physicians who were treating these patients identified that there was something going on, that there were cases that were clustered together,” said Fraser, who had only been a U.S. Centers for Disease Control epidemic intelligence service officer — a sort of disease detective — for about a year when he began the public health investigation. Officials from every level of government contributed to the investigation.
Investigators discovered legionella bacteria in January 1977, confirming the existence of legionnaires’ disease, Fraser says, a severe, treatable, but potentially fatal pneumonia caused by inhaling the bacteria through water vapour — like that coming from an air-condition system.
“This is a disease of progress,” he said.
An introduction to legionella
At first, however, investigators thought the outbreak might be swine flu or a viral infection, according to Fraser.
The team wasn’t clear where the disease came from, nor how it spread. It resulted in more than 200 infections and 30 deaths before the bacteria was identified.
Legionella is present in both natural and artificial water sources, including modern technology like HVAC or air-conditioning systems.
“Warm water is not something that the world had much of before humans [started] making machines,” Fraser said. “We learned an important way that modernization is increasing our risk of exposure to environmental pathogens.”
In the past two years, an outbreak of legionnaires’ disease in London, Ont., has left four people dead and sent dozens of people to hospital before the source was found. CBC’s Jennifer LaGrassa breaks down how health officials found where it started and why it took so long to trace.
The legionnaires’ investigation never pinpointed the exact source of the outbreak, but Fraser’s hypothesis is that a cooling tower on the roof of the hotel where the conference was held may have housed the legionella bacteria.
“By the time we had the tools for culturing the water from that system, the system had long since been shut down and cleaned,” Fraser said.
Nonetheless, the investigation led to the development of better environmental management standards, according to University Health Network infectious diseases physician Dr. Alon Vaisman.
Today, large buildings have stringent inspection and cleaning practices to prevent the conditions that allow legionella bacteria to flourish. Regulators also set minimum standard temperatures for hot and cold water in pipes and fixtures.
And the Public Health Agency of Canada recommends keeping home water heaters at a minimum of 60 C to prevent the growth of legionella bacteria.
“These standards that have been developed for legionella,” Vaisman said. “They also help prevent the transmission of other pathogens, which are transmitted through different routes.”
Media lessons learned
While infectious disease experts say the 1976 legionnaires’ disease outbreak offered lessons on how to prevent the transmission of infectious diseases, journalism professor Sarah Everts says it’s a textbook example of what not to do when reporting on public health emergencies.
“One of the things that really struck me as I read about legionnaires is just how much the misinformation just immediately spiked,” said Everts, an associate professor at Carleton University and a fellow at the Science History Institute in Philadelphia researching the 1976 legionnaires’ outbreak.
At the time, she said, media reporting largely added to the anxiety.
“Magazines were calling it, the Philly killer,” she said. “There were claims that it was Soviet spies. There were claims it was the CIA. There were claims it was a biological weapon that had accidentally been released by the U.S.”
Fraser also remembers the media being less than helpful.
During the initial phases of the investigation, he says reporters were often with him in the room while he conducted meetings over the phone, and they wrote about the various scenarios being discussed.
“Many of the stories had to do with hypotheses that scientists or the public had come up with that we hadn’t yet ruled out,” he said.
But the public health lessons learned from the 1976 legionnaires’ outbreak can be seen in effect as recently as the hantavirus outbreak on the MV Hondius cruise ship, Vaisman said.
“Everything has been done to a very high degree of care, and to some degree, also precision,” he said.
“I think most people would say it’s been very successful on many fronts considering how quickly it develops as well.”
