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Final report on the provincial outbreak of measles in 2011

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As of March 21, 2012 (12 p.m.), after more than three incubation periods without any new confirmed cases of measles being reported, the Bureau de surveillance et de vigie (BSV) has officially closed the provincial measles outbreak that began during the winter of 2011.

Report on epidemiological surveillance

During 2011, several hundred cases (n=776) of measles were reported to the BSV, compared to an usual average of 0 to 2 cases per year.

This outbreak of measles lasted from the 8th of January to the 22nd of December 2011 (the dates of the first and last confirmed cases reported). From January to March, 12 cases were reported but it was in April that sustained local transmission started, first in schools and then in communities. The vast majority of cases (88 %) occurred between May 1st and July 30th, 2011 (see figure 1). In September, with the return to school, transmission resumed. This was relatively circumscribed and quickly brought under control.

The last reported confirmed case occurred in a European travelling to Quebec. The infection was acquired in the country of origin.

Figure 1 - Distribution of cases of measles (n=776) by date of onset rash and confirmation status, Province of Québec, 2011

Source: Bureau de surveillance et de vigie, DPSP, MSSS, May 2nd, 2012 (12 p.m.).

A total of 776 cases were reported (725 confirmed cases and 51 clinical cases). Ten regions declared at least one confirmed case (see table 1). A very high proportion of cases (69 %) was concentrated in Mauricie et Centre-du-Québec region (RSS 04). With 19 % of total cases, the Montérégie region (RSS 16) comes in second place among the most affected regions.

Table 1 - Final report on the provincial outbreak of measles - Number of cases (confirmed and clinical) reported by region of residence, Province of Québec, 2011

  Total cases reported
Region of residence
Number
%
01 - Bas-Saint-Laurent
1 0,1
02 - Saguenay–Lac-Saint-Jean
2 0,3
03 - Capitale-Nationale
31 4,0
04 - Mauricie et Centre-du-Québec
538 69,3
05 - Estrie
26 3,4
06 - Montréal
15 1,9
07 - Outaouais
0 0,0
08 - Abitibi-Témiscamingue
0 0,0
09 - Côte-Nord
0 0,0
10 - Nord-du-Québec
0 0,0
11 - Gaspésie–Îles-de-la-Madeleine
0 0,0
12 - Chaudière-Appalaches
5 0,6
13 - Laval
0 0,0
14 - Lanaudière
3 0,4
15 - Laurentides
9 1,2
16 - Montérégie
145 18,7
17 - Nunavik
0 0,0
18 - Terres-Cries-de-la-Baie-James
0 0,0
Résidents hors Québec
1 0,1
Total 776 100

Source: Bureau de surveillance et de vigie, DPSP, MSSS, May 2nd, 2012 (12 p.m.).

Case characteristics

The majority of the 776 cases occurred in young people 10 to 19 years old, with the average age being 15.2; 1 out of 9 cases (11 %) required hospitalization. No death were reported. Complications were reported in 64 cases (8 %), most being respiratory (27 cases of pneumonia).

Vaccination status of cases

A number of 615 cases (79 %) were not considered protected (immune) for the following reasons:

  • Had not received any dose of vaccine,
  • Had no proof of vaccination,
  • Were not eligible for vaccination,
  • Did not know that they had already been vaccinated or whether they had the disease.

Among them were 29 children less than one year old, which is the minimum age to receive a first dose of vaccine.

Measles vaccination in Quebec

According to regular vaccination schedule, the first dose of MMR (measles-mumps-rubella) vaccine should be administered at 12 months of age and the second at 18 months. The efficacy of the MMR vaccine against measles reaches 95 % when both doses are administered, and protection against the disease is probably long-lasting.

With the goal of continuing the objective of eliminating measles in Québec, from autumn 2012, proofs of immunization will be collected and vaccination offered among unimmunized children in kindergarten and students in Elementary school grade 4 and in Secondary 3.

To find out more about measles and the vaccine against measles, see the Questions and answers about measles section.

Bureau de surveillance et de vigie
Ministère de la Santé et des Services sociaux
August 31st 2012 (12 p.m.)

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