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Vaccine-Preventable Diseases
Measles

Updated: November 14, 2007

Description and Symptoms

In recent months, cases of measles have been reported in Quebec. Provincial and local health authorities are leading the investigation into the outbreak and managing the response with support from the Public Health Agency of Canada.

Occurrence

During the XXIV Pan American Sanitary Conference in September 1994, representatives from Canada and other Pan American Health Organization nations resolved to eliminate measles in the World Health Organization region of the Americas. Shortly thereafter, in 1995, Canada's Conference of F/P/T Deputy Ministers of Health endorsed a national goal of measles elimination.

Nationally, sustained transmission has been eliminated by the current 2-dose measles vaccination programs and high vaccine coverage in the general population. The 2004 National Immunization Coverage Survey (NICS) estimates that 94% of two year-olds have received one dose of measles vaccine and that 79% of seven year-olds have received at least two doses. Epidemiological and virological evidence suggests that endemic transmission of measles has been mostly interrupted since 1998; however, as expected, imported cases continue to occur. Secondary spread from these cases is usually self-limited and involves the few Canadians who are still vulnerable due to under-vaccination or opposition to vaccination.

Canada has had national, active measles surveillance in place since 1998. All provinces and territories report confirmed cases of measles weekly to the Public Health Agency of Canada who in turn report weekly to the Pan American Health Organization. As of the week starting November 4, 2007, there were 101 measles cases reported this year in Canada: Quebec (95), Alberta (3), and British Columbia (3).

Over the past five years, there has been an average of 10 measles cases each year in Canada with clusters of approximately 4 cases. The last large outbreak happened in the year 2000. It was centred in Alberta and involved nearly 200 individuals; nearly all of them un-immunized for religious or philosophical reasons. The initial cases were imported from Mexico and Bolivia. 

Prevention

The virus can be spread for about four days before and until about four days after rash onset. Health officials have implemented a public information campaign to advise patients, the general public and health care providers on the appropriate control measures. People experiencing measles symptoms are advised to call before going to a doctor's office or clinic as a precaution to assist health care providers in preventing further spread of the disease.

Questions and Answers

1. What is the cause of the current outbreak in Quebec?
2. What steps have been taken to control the measles outbreak?
3. What is the Government of Canada doing to assist?
4. Why is the number of cases on the Quebec website different from the number of cases on the PHAC website?
5. What are the symptoms of measles?
6. How is the disease transmitted?
7. Why is measles a concern?
8. Are outbreaks of measles common in Canada?
9. Why do outbreaks still occur?
10. Why was a second dose of the vaccine introduced?
11. When is the vaccine administered?
    
    

Q1. What is the cause of the current outbreak in Quebec?

The investigation indicates that cases are occurring among individuals who are either not immunized, or who are under-immunized because they did not receive two doses of measles vaccine. To minimize the risk of contracting the disease, all Canadians should maintain up-to-date immunization for themselves and their families.

Q2. What steps have been taken to control the measles outbreak?

Public health authorities in Quebec are leading the investigation and managing the response. This includes actively searching for and managing cases as well as tracing contacts and offering vaccination or preventative medication as required. Authorities continue to advise the public of the ongoing measles activity and are encouraging individuals to update their immunization, if necessary.

Q3. What is the Government of Canada doing to assist?

The Public Health Agency of Canada (PHAC) maintains a weekly measles surveillance system. All provinces and territories have been encouraged to remain vigilant in monitoring for measles activity within their regions and reporting any cases to the Agency. As well, the Public Health Agency notifies appropriate authorities regarding exposure settings involving inter-provincial or international travel. PHAC will continue to work with provinces and territories by providing technical advice and assisting with laboratory testing.

Q4. Why is the number of cases on the Quebec website different from the number of cases on the PHAC website?

Only confirmed cases which meet the national case definition are being counted and reported by PHAC. Probable and suspect cases still need to be identified for prompt and appropriate medical and public health management (e.g. diagnosis, specimen collection, laboratory testing, clinical care, as well as public health reporting, follow-up and intervention). A confirmed case meets one of two criteria: (i) laboratory-confirmation of measles infection OR (ii) clinical compatibility with measles infection and an epidemiologic link to a laboratory-confirmed case.

Q5. What are the symptoms of measles?

Symptoms of measles typically appear in two stages. The first signs are the onset of fever followed by red eyes (conjunctivitis), runny nose, cough and white spots on the inside lining of the mouth. In the second stage, a characteristic red blotchy rash appears on the third to seventh day, beginning on the face and becoming generalized lasting for 5-6 days.

Q6. How is the disease transmitted?

Measles is highly contagious, spread by contact with an infected person through coughing and sneezing.

The disease can be transmitted from an infected individual four days prior to the onset of the rash until four days after. Fever usually begins about 10 days after and rash usually begins about 14 days after exposure.

The virus is present in the mucus of the nose and the throat of an infected person. When that person sneezes or coughs, droplets spray into the air and land on surfaces. The droplets can infect other individuals when they breathe or touch their hands to their face after handling an infected surface. Airborne transmission has been found in closed areas (like a waiting room) for up to two hours after a person with measles has been present. The disease is so contagious that almost every exposed individual, if not adequately immune, will contract the virus.

Q7. Why is measles a concern?

Measles is a severe respiratory tract infection caused by a virus. Measles infections can cause complications including ear infections, pneumonia, encephalitis and seizures. Generally the disease is more severe in infants and adults than in children. Measles during pregnancy can result in a higher risk of premature labour and low infant birth weights.

In Canada, death is estimated to occur once in 3,000 cases. In developing countries, the rate of death from measles is much higher. Each year, nearly one million measles deaths occur among children worldwide. Canada, along with the other member states of the Pan American Health Organization, have endorsed the goal to eliminate measles in the Western Hemisphere.

Q8. Are outbreaks of measles common in Canada?

Occurrence of the disease has declined markedly since the introduction of the measles, mumps and rubella vaccine – the “MMR” vaccine. Prior to the introduction of the vaccine, there were an estimated 300,000 to 400,000 cases of measles in Canada each year. The vaccine, and the introduction by all provinces and territories of a second dose to vaccination programs, has resulted in a significant decline in the disease. Over the past five years, there have been an average of 10 measles cases a year reported in Canada.


Q9. Why do outbreaks still occur?

Measles remains endemic in several countries around the world. It is a highly infectious disease, easily transmitted to individuals not adequately protected through immunization or history of disease. In general, there is high two-dose vaccine coverage among Canadians and outbreaks are not frequent. The last large outbreak was centred in Alberta in the year 2000. It involved about 200 individuals in a population largely unimmunized for religious or philosophical reasons.

A 2004 immunization coverage survey estimated that 94% of two year-olds have received one dose of measles vaccine and that 79% of seven-year-olds have received two doses of the vaccine.

A small proportion of adults born since 1970s may not have received a second dose of the vaccine when the two-dose vaccine schedule was introduced in the mid-1990s. To minimize the risk of measles exposure, a second dose of MMR vaccine is recommended for adults born after 1970 who are at the greatest risk of exposure. This includes students at post secondary institutions and health care workers.

Q10. Why was a second dose of the vaccine introduced?

Between 1989 and 1995, in spite of very high vaccine coverage, there were many large outbreaks involving mainly children who had received one dose of measles vaccine. It was estimated that 10% to 15% of immunized children remained unprotected after a single dose given at 12 months of age, a proportion large enough to allow the circulation of the virus to continue in Canada.

In 1996/97, every province and territory added a second dose to its routine schedule, and most conducted catch-up programs in school-aged children with measles or measles/rubella vaccine. This reduced the proportion of children vulnerable to the virus to a such a negligible level that endemic viral transmission could not be sustained.

Q11. When is the vaccine administered?

Two doses of the MMR vaccine are recommended for children to provide adequate protection from the virus. One dose is to be administered on or after the first birthday; the second dose should be given after 15 months of age and before school entry. A second dose of MMR vaccine is also recommend for Canadians at greatest risk of exposure, including travellers to areas of the world where measles is endemic, health care workers, military recruits and students at post-secondary institutions.