Public Health vexed by bacterium
Toronto agency can’t find cause of 78% spike in M. avium cases
There has been a mysterious 78-per-cent jump in the number of Torontonians testing positive for a bacterium that can cause chronic lung infections in people with pre-existing lung problems and weakened immune systems, the Star has learned.
According to Public Health Ontario, an average of 66 new cases of residents testing positive for Mycobacterium avium have appeared each month between June 2014 and June 2015 — the most current numbers available. That’s up from an average of 37 new monthly cases in each of the preceding 49 months.
“There is cause for concern here, but certainly no cause for panic,” said Dr. Ray Copes, the agency’s chief of environmental and occupational health, explaining that not everyone infected with the bacterium becomes ill.
“You have to ask what’s going on . . . We are not entirely sure of that yet,” he said.
Toronto Public Health has been unable to find the source of the increase and has stopped investigating, said Dr. Christine Navarro, associate medical officer of health.
Respirologist Dr. Ted Marras, an expert in treating those infected with M. avium, said he’s “disappointed” by that.
Extrapolating from previous research, about 33 Torontonians may be getting sick from it monthly, he said.
These are typically individuals with un- derlying susceptibility such as elderly people, those who are HIV-positive and those with pre-existing lung problems, said Marras, director of the nontuberculous mycobacterial clinic at Toronto Western Hospital and assistant professor of medicine at the University of Toronto.
Most who become ill suffer lung damage and develop recurrent lung infections.
Marras said he would like to see the spike in cases further investigated. Ideally, he would like a sample of patient records analyzed to determine exactly how many of those who test positive are becoming ill.
M. avium is an environmental organism found widely in soil and water.
It is most commonly transmitted by inhaling droplets of water that contain the organism, with municipal water supplies typically being the original source, Copes explained.
“This is not something that you get through drinking water as much as (through) water that is aerosolized that people could inhale. That does happen with showers, hot tubs and a number of other uses of municipal water,” Copes explained. He emphasized that Torontonians should not be afraid to drink tap water.
“It would be really inappropriate for people to stop drinking water in Toronto because of this. I’ve known about this, and I am still drinking Toronto water,” he said.
The organism is almost always present in municipal water supplies and total eradication is unlikely, Copes explained.
The bacteria tend to grow in biofilms that line large water pipes in municipal water distribution systems and even smaller pipes in individual buildings, he said.
Many jurisdictions in the developed world have seen a gradual increase in positive results over the last decade, but a sudden spike is unusual, he continued.
“You can see a point in time when something changes,” Copes said, referring to June last year. “There really does seem to be something different happening here.”
Asked whether Toronto Public Health has ruled out the city’s water supply as the source of the increase, Navarro said: “TPH found there was no pattern in where people who tested positive for the Mycobacterium avium were located in the city, or any clustering that could be related to environmental exposures such as water supply, water temperature, water main replacements or changes in water treatment.”
M. avium is not a reportable disease, meaning health practitioners are not required to report cases to municipal public health units, as they are with food-borne illnesses and communicable diseases.
Testing for the bug is done through sputum samples by Ontario Public Health, typically as part of a bigger workup of tests ordered by treating physicians. Only those physicians would know if patients who tested positive were ill. M. avium is less likely to cause illness in healthy people. Symptoms of M. avium lung disease typically include cough, production of sputum and fatigue. Sometimes patients suffer shortness of breath, chest pain and weight loss. For most, it is chronic.
“It usually ends up in some sort of lifelong condition that at times can become very severe. In some patients, it can become life-threatening and progressively destroy more and more lung tissue,” Marras said, adding that some patients suffer only minor symptoms. Treatment is difficult and consists of taking three different kinds of antibiotics, he noted.
Compounding the problem is that over the summer, there was a shortage of one of the main drugs used to treat patients. The Canadian Drug Shortage Database shows that drug manufacturer Valeant Canada experienced delays in shipping the drug, ethambutol.
It was back in stock by September.