Charting the Rise of Measles in Canada
Understanding this highly contagious viral infection.
In a way, measles is like an airplane crash: it makes the news because it’s uncommon. Still, 2014 saw a higher-than-average rate of measles within our borders, according to Public Health Canada. In recent years, there have been several significant outbreaks-including one in Quebec in 2011, with 725 cases.
The signature symptom of the measles is aesthetic: a blotchy rash. More dangerously, it weakens the immune system for weeks, which can lead to complications. On average, out of every 1,000 measles patients in a developed country, 100 will get pneumonia or another opportunistic infection; one will get a swollen brain with possible brain damage; and one to two will die.
With such a low mortality rate, measles may not sound like a major threat, but its contagiousness amplifies its impact. The virus remains alive and can be spread through the air or on surfaces for up to two hours-you can easily catch it from someone coughing or sneezing.
If surrounded by people without immunity from prior infection or vaccination, each patient would give measles to around 17 others. Because of these factors, the virus used to affect the majority of Canadian children-and kill around 300 each year-before the vaccine became available in the 1960s.
Elsewhere, measles still kills: in 2013, there were 145,700 related deaths worldwide, most of them children. That said, the young are increasingly being vaccinated-the 2013 death count was 75 per cent lower than it had been in 2000. Indeed, the World Health Organization (WHO) is targeting measles for global eradication, a realistic goal given that humans are the virus’s only natural host.
But until the WHO succeeds, there is a very real risk of bringing measles home from abroad. Most of this country’s flare-ups begin with a Canadian who recently travelled internationally.
Although Canada’s overall vaccination rate remains high, there are certain places where it’s not high enough-the WHO recommends 95 per cent to provide “herd immunity.” For example, one of the recent outbreaks in British Columbia’s Fraser Valley centred around a religious group that shunned vaccines.
Measles-mumps-rubella (MMR) shots don’t guarantee that a child won’t get measles, but they bring the risk down to almost nil. The more people who go in for it, the lower the chance the virus will spread to anyone-including babies who are too young for the vaccine and the minority of people who don’t respond to it. Covering immunity gaps would go a long way toward improving our spotty infection record.