Legionnaire’s Lessons

The cause of 17 deaths due to respiratory illness at a Toronto senior’s home turned out to be an isolated event, but the incident made headlines worldwide as it brought to mind the specters of SARS and the bird flu. The identity of the disease remained a mystery for more than 10 days until Thursday, Oct. 6, when Toronto Public Health officials disclosed that it had been identified as Legionnaire’s Disease, a rare form of pneumonia.

The disease did not move far out of the Seven Oaks Home for the Aged, where the episode began, because Legionella Pneumophilia, the bacterium that causes it, cannot be spread from person to person. Outbreaks of Legionnaire's Disease are not overly common in North America, but the bacteria can flourish in warm water conditions such as hot water tanks and ventilation systems in large buildings.

In the case of Seven Oaks, neither of these possible breeding sites for the disease was ruled out. The home’s ventilation system was shut down and inspected, and bottled water was used at both the home and at the adjacent child care centre while the home’s on-site water system was investigated and later flushed, said a Toronto Public Health press statement. Both systems are now back in operation, but the air intake mechanism remains under scrutiny.

Legionnaire’s is often mild in form, and becomes lethal in 5-30% of cases of people with pre-existing weakened immune systems and severe medical problems. Indeed, all of the 17 that died at Seven Oaks had medical conditions prior to contracting the disease. In total, 71 residents, 23 staff and 14 visitors were infected. With antibiotic treatment and preventative care at the home, it appears that the disease is dying out.

Legionnaire's Was Initially Ruled out

What is disturbing about this case is that, alongside nasal swab and blood tests which excluded influenza and SARS, 23 urine tests for Legionnaire’s Disease among Seven Oaks residents came up negative. Until Thursday, Legionnaire’s had been excluded along with the others as a possible cause of the respiratory illness.

Microbiologist Dr. Allison McGeer, an Infectious Disease Consultant and Director of Infection Control at Mt. Sinai Hospital in Toronto, is working hard to find out why.

“It’s possible that the patients tested weren’t ‘positive’ yet,” she says.

McGeer lists several other possible causes, including faulty testing (which she deems highly unlikely due to the stringent quality controls that were used), or perhaps that the sample of patients tested may have had a less severe virus that was also going around the home, not Legionnaires.

“We tested 23 people…that’s why it’s so distinctly odd. We think it’s possible it’s a new serotype.”

Here McGeer hits upon advice that appeared on the ProMED-mail website of the International Society of Infectious Diseases, which tracks infectious diseases globally.

Dr. Stever Berger of the Tel Aviv Medical Centre, upon reading that Legionnaire’s had been discounted on the basis of urine tests, noted,

“Most such tests are designed to detect only Legionella Pneumophillia serogroup 1. Additional procedures, such as culture and serology, should be performed in order to rule out other strains of Legionella.”

Only further tests, no doubt being pursued by McGeer, will tell if he is correct.

Implications for Bird Flu

Legionnaire’s was only discovered because of dedicated preparation of cultures and in-depth testing, perhaps due to the initial insights of scientists such Dr. Berger. This raises the prospect that the bacterium was initially discounted because scientists were not testing for the right strain, or perhaps couldn’t test properly because a new strain had evolved sufficiently to not be recognized by the basic tests. That, in turn, stands as a stark reminder that the same can happen in much more serious situations.

Government officials worldwide have felt the pressure to ensure that the specter of H5N1, the lethal-to-humans variant of bird flu, does not appear on their doorstep – even the suggestion of it is to be avoided. For example, in early August, Kazakh officials were cited by the China Post as denying the newfound bird flu in the country was H5N1, only to have to backpedal on the statement later.

Officials have a lot of cause for worry: The SARS debacle in Toronto in 2003 cost the city 44 lives and an estimated $1 billion in lost tourism revenues. On Thursday, a Toronto newspaper headline eagerly reported that the senior’s home disease was “not SARS.”

In contrast to Legionnaire’s Disease, H5N1 Avian Flu is highly contagious, meaning that quick testing and isolation of the patients and disclosure of the cases to the global community are of paramount importance. Avian influenza also mutates at high rates, so it is possible that identifying a lethal and contagious strain could take time, as it did in the Legionnaire’s example. Add to that the pressure which governments experience to avoid “premature” disclosure of the occurrence of diseases such as bird flu, and you have a genuinely troubling situation.

At the recent Washington, D.C. global conference on bird flu, delegates from 80 nations discussed ways to minimize the damage that could be wrought by H5N1. Paula Dobriansky, US Under Secretary of State for Democracy and Global Affairs, was quoted by AFP as saying,

"If avian flu does mutate to allow easier human to human transmission, the results would be catastrophic locally, regionally, and globally." She added, "Working through a global partnership offers we think the best chance, perhaps our only chance, of confronting this threat effectively on all fronts.”

Back in Toronto, Dr. Barbara Yaffe, Director of Communicable Disease Control at Toronto Public Health, says that Toronto’s experience with SARS has helped the city prepare for febrile respiratory illnesses such as bird flu.

“We learned a lot from SARS. Communication and coordination between the stakeholders, for example hospitals, Public Health, labs…have improved a lot.”

She says that the city’s post-SARS Provincial Infectious Disease Advisory Committee, a team of experts on infectious diseases, can act quickly to address any sudden outbreak.

“There are always lessons learned; all the different stakeholders will get together and debrief at the end. It’s standard practice, but it’s not over yet.”

It’s clear that Toronto health authorities are working hard to be on the ready for any new outbreaks, such as the expected bird flu pandemic. How effective will they be? Unfortunately, only time can tell.