There have been more than a dozen suspected opioid overdose deaths in the city over the last week, an alarming increase which Toronto Public Health says represents the “worst cluster” of fatalities that it has seen since it began tracking the data three years ago.

Toronto Public Health issued a warning on Friday afternoon after paramedics reported a total of 15 suspected overdose deaths involving opioids between July 9th and July 17th.

The high number of fatal overdoses reported in just over a week surpasses the 13 that were reported in all of June and nears the average of 18 that have been reported on a monthly basis so far in 2020.

In its warning, Toronto Public Health said that there has been a sustained increase in fatal overdose calls since March, outside of a slight dip in June. It says the calls highlight “the unpredictable nature of the drug supply.”

“Previous drug checking data show that the unregulated drug supply in Toronto contains unexpected drugs of concern, including benzodiazepines,” the warning from Toronto Public Health states.

Toronto Public Health says that the recent rash of fatal overdose calls were “largely in the downtown and north-west areas of the city.”

It said that while there have been reports from the community about overdoses involving crack cocaine as well as fentanyl in recent weeks, it is unclear what drug or drugs are to blame for the most recent fatalities.

In a subsequent message posted to Twitter, Toronto Public Health says drug users should “try not to use alone,” given the increase in overdoses.

Since 2017, paramedics have attended 68 overdose calls a week on average with about three of those resulting in death.