PHAC recently issued a travel advisory on measles globally
as a reminder to travellers to be sure about immunity. PHAC
travel advisory. International travel has become the major
contributor to importation of measles into Canada.
Then as this posting went up, a report of spread of measles in the US related to the Superbowl. Measles and Super bowl with at least 14 cases so far and more spread is likely given the number exposed
Then as this posting went up, a report of spread of measles in the US related to the Superbowl. Measles and Super bowl with at least 14 cases so far and more spread is likely given the number exposed
Great advances have been made in controlling measles in
Canada, so much so we often forget the devastation that the disease reaped
havoc prior to the ‘60s when 250,000-400,000 cases occurred in Canada annually. Measles remains the number one vaccine
preventable cause of death internationally with some 150,000-200,000 deaths per
year. The embedded graph provides the Canadian
view of measles control, something that is replicated in most developing
countries.
2002 the Americas were declared as measles free for
indigenous spread. Already in 2012 there
have been nearly a 1000 cases in the Americas alone PAHO
weekly reporting
While it is difficult to be sure on numbers, Canada had 750
cases in Quebec in 2011 Quebec
measles outbreak update, 79% of which were underimmunized. BC in the wake of the 2010 Olympics saw 82
cases. Both outbreaks sparked by
importations into the country and then sustained local transmission. Both outbreaks speak to the vulnerability of
Canada that despite great immunization programs, sustained transmission can and
does occur.
The reproductive number of measles is estimated at 12-18 –
meaning every case could potentially infect 12-18 non-immune persons. Of course the propagation of the disease will
occur when the probability that each case contacts at least one other
non-immune person. When population
immunity levels begin to drop to where one in 20 is susceptible then the likelihood
that each case will transmit to one or more people becomes more likely and propagation
will occur. (Simply put, but a close
estimate). Even the best 2-dose coverage levels in
Canada are just over 90%, with about half of the underimmunized having had one
dose of vaccine.
Despite the international efforts to contain measles,
dissemination and propagation continue to occur. It remains a public health emergency and
requires immediate mobilization to contain importations – just that the event would
appear to be getting more frequent and the consequences are not just a few
cases, but into the tens and hundreds before control is achieved. On the positive side, the first decade of
this century saw global measles deaths reduced by nearly 80% - short of the
objective, but a huge improvement.
More is available on measles in Canada at PHAC
measles site, but as is typical of PHAC, that sense of declining success
and building urgency is lacking.
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