Doctor, virologist caution against attending large public gatherings if unvaccinated against measles

With the number of measles cases in Manitoba swelling, experts caution those who aren't vaccinated for the disease to stay away from large public gatherings until the outbreak settles down. 

The warning comes after Manitoba's government said those who attended the AG Days indoor farm show in Brandon late last month might have been exposed to measles. 

About 35,000 people attended the annual event at the southwestern Manitoba city's Keystone Centre between Jan. 20 and 22. Those who visited hotels, restaurants and shops in the city during the three-day event were also possibly exposed to the virus, according to Manitoba public health. 

"It's absolutely terrifying," said Dr. Philippe Lagacé-Wiens, a medical microbiologist and physician at St. Boniface Hospital.

"In a closed space, 90 per cent of people who are susceptible will catch measles if there's a person who's infectious and goes into that room."

With symptoms of measles becoming physically evident sometimes weeks after getting infected, a person with the disease could spread it unknowingly.

"This chain of transmission going downstream is when you've got that many exposed people. It is very concerning," he said.

In January, Manitoba reported the highest monthly count of confirmed measles cases since the outbreak began in February 2025. 

As the illness continues to circulate at this extent, people are more likely to be exposed to the disease in larger groups, and those who aren't vaccinated have a high chance of getting infected, Lagacé-Wiens said. 

Measles can stay in the environment hours after an infected person has been in a space, and  Lagacé-Wiens said that unlike with COVID-19, physical distancing or masks do little to protect someone from contracting it.

"The really big message is if you're not vaccinated against measles or you have any kind of measles-like symptoms, don't go to these festivals," he said. 

The same message should also be relayed by event and festival organizers, Lagacé-Wiens said. 

Visible signs that remind people how measles can spread at large events, and the importance of staying home if presenting symptoms are an alternative, he said. 

Angela Rasmussen, a virologist and principal scientist at the Vaccine and Infectious Disease Organization in the University of Saskatchewan, said herd immunity is no longer an option to protect unvaccinated people from contracting the virus.