Organizers of the Prospectors and Developers Association of Canada (PDAC) informed its more than 23,000 attendees that one person who attended the event on March 2 and 3 has tested positive for COVID-19, commonly known as the coronavirus.

An email was sent to attendees explaining that a man in his 50s from the Sudbury region of Canada tested positive. PDAC is the largest annual mining convention in North America and this year Canadian Prime Minister Justin Trudeau made an appearance as did mining officials from Brazil, Chile, Peru and Canada.

“As we know, that is a massive international conference with many countries represented and many, many individuals there,” Dr. Penny Sutcliffe, medical officer of health at the local health authority in Sudbury, said in a news conference on March 11.

Bloomberg reported that the northern Ontario city of Sudbury, the center of the country’s nickel-mining industry, is where the unidentified man went to hospital on March 7 after attending PDAC March 2 and 3. Sutcliffe said potentially hundreds of people from Sudbury attended the conference.

“Our focus now is on breaking the chain of transmission to limit the spread of infection,” Sutcliffe said in an earlier statement. “As a precautionary measure, we are asking those who attended PDAC 2020 to monitor for symptoms for 14 days.”

Trudeau, unveiling C$1.1 billion ($800 million) in aid to buffer the Canadian economy from the virus, said he hasn’t been tested but is following public health guidelines for those who’ve attended large events. That can include monitoring health for symptoms.

Other mining executives and government officials who attended PDAC included Ontario Premier Doug Ford, Chilean Mining Minister Baldo Prokurica, Rick Rule, chief executive officer of Sprott U.S. Holdings, top mining officials from Brazil, and the heads of mining groups of the capital market divisions of several Canadian banks.

“In general, large gatherings with transient interactions including walking by a person who may be infected COVID-19 or briefly being in the same room with that person are considered a low risk,” Eileen de Villa, medical officer of health for Toronto, said in a statement.

PDAC ran one week after the MineXchange SME 2020 Annual Conference in Phoenix, AZ. Coronavirus was a much-talked about topic at both conventions. Handshakes were replaced with fist and elbow bumps and hand sanitizer was in ample supply. Since then, a number of professional conferences around the world have been postponed or canceled as large gatherings of people have been discouraged. On March 11, the National Basketball Association suspended its season. Fears of the spread of the virus has wreaked havoc on the stock markets around the world.