Vaccine-Preventable Diseases Measles

Measles

Measles is a highly infectious disease caused by the measles virus and is characterized by a red, blotchy rash that begins on the face. It is spread through direct contact with or inhalation of the secretions from an infected person's nose or mouth. Measles affects all age groups and can be prevented by a vaccine. The National Advisory Committee on Immunization (NACI) recommends that children receive a first dose of measles vaccine at 12 months of age followed by a second dose at either 18 months or at 4 to 6 years of age

About Measles

Agent of disease

Measles is caused by the measles virus, a member of the genus Morbillivirus of the family Paramyxoviridae.

Symptoms

Symptoms of measles begin 7 to 18 days after infection and include fever, runny nose, drowsiness, irritability and red eyes. Small white spots (known as "Koplik's spots") can appear on the inside of the mouth and throat. Then, 3 to 7 days after the start of the symptoms, a red, blotchy rash appears on the face and then progresses down the body. Complications include diarrhea, pneumonia and infections of the brain. In developed countries 2 to 3 cases per 1,000 result in death. This increases to 3 to 5 cases per 1,000 in developing countries.

Period of communicability

The incubation period for measles is about 10 days, but may be 7 to 18 days from exposure to onset of fever.  The rash usually appears 14 days from exposure although it can seldom appear as late as 19 to 21 dates from exposure to the measles virus.  Infectiousness begins from 1 day before the beginning of the prodromal period (usually about 4 days before rash onset) to 4 days after appearance of the rash.

How it is transmitted

The virus is transmitted by airborne droplets or direct contact with nasal or throat secretions of infected persons. Less commonly, the virus spreads through contact with articles freshly soiled with nasal and throat secretions.

Worldwide distribution

Measles occurs throughout the world and remains a serious and common disease in developing countries. According to the World Health Organization , measles is a leading cause of vaccine preventable deaths in children worldwide. The global goal was to reduce mortality due to measles by 90% by 2010 (compared with levels in 2000). This goal was not reached. By 2008, the global mortality of measles has been reduced by 78%, from an estimated 733 000 deaths in 2000 to an estimated 164 000 deaths.

Measles was eliminated in the WHO Region of the Americas in 2002 with the last endemic measles case occurring on November 16, 2002. Since that time, there have been small numbers of imported and import-related cases in the Americas: the annual count ranged from a low of 85 in 2005 to a high of 253 in 2010. These cases have resulted in limited secondary spread. However, in 2011, this region has reported the highest number of measles cases since the virus was eliminated, with the majority of these cases associated with a large outbreak in Quebec, Canada.

Outside of the Americas, measles activity remains high. As of October 2011, there were over 26,000 cases in the WHO European Region with the highest number reported in France (more than 14000 cases). There have been 11 measles-associated deaths in the Region. Large outbreaks have also occurred in Africa, mostly in the Democratic Republic of the Congo, with more than 106,000 cases and 1100 deaths

Prevention and control

Measles can be prevented by immunization. Immunization of all children is recommended at 12 months of age as part of a combined vaccine containing measles, mumps and rubella (MMR); with a second dose at either 18 months or at 4 to 6 years of age. For further information about the MMR vaccine and its use in adolescents, adults and special populations, please refer to the most recent version of the Canadian Immunization Guide.

Any suspect measles cases, particularly those with travel history to areas with endemic or epidemic measles, should be reported as soon as possible through local public health. Patients should be isolated for 4 days after appearance of the rash. Searching for and immunizing exposed susceptible contacts can limit the spread of disease.

Epidemiology in Canada

Canada has made great progress in its goal of measles elimination, and endemic transmission of measles has been interrupted by high vaccine coverage as a part of routine infant and childhood immunization programs.  There have been no indigenous cases of measles reported in Canada since 1997. However, imported cases continue to occur. Secondary spread from these imported cases has been self-limited and involves Canadians who are still vulnerable due to lack of immunizations or only partial immunization (i.e. only one dose of vaccine).    The largest outbreaks have occurred in isolated groups that are philosophically opposed to immunization with very limited secondary transmission of measles in the general population. Between 2002 and 2010, a total of 327 confirmed cases of measles were reported in Canada, with an average of 11 cases annually except in 2007 (102 cases), 2008 (62 cases) and 2010 (99 cases). The high numbers of cases in those three years were mainly due to outbreaks in Quebec, Ontario and British Columbia respectively (please see Recent Outbreaks for more detailed information).

Before the introduction of the vaccine in 1963 to 1964, measles occurred in cycles with an increas­ing incidence every 2 to 3 years. At that time, an estimated 300,000 to 400,000 cases occurred annually. Since the introduction of vaccine, the incidence has declined considerably in Canada (see Figure 1). 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 the 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 circulation of the virus.

In 1996/97, every Canadian province and territory added a second dose of measles-containing vaccine to its routine immunization schedule, and most conducted catch-up programs in school-aged children with measles or measles/rubella vaccine. This intervention achieved vaccine coverage for the second dose in excess of 85%, reducing the proportion of vulnera­ble children to such a negligible level that viral transmission has not been sustained.

FIGURE 1:  Measles – Reported Incidence, Canada 1924-2011

Note: measles was not nationally notifiable between 1959 and 1968. The incidence rate for 2011 is annualized up to August 31, 2011.

Figure 1 - Text Equivalent

Recent Outbreaks

A recent outbreak in Quebec beginning in April 2011 has resulted in 676 confirmed and 73 probable cases occurring between April 3, 2011 and November 2, 2011. As of November 2, 2011 the outbreak is ongoing. For up-to-date information regarding this outbreak, please consult the Quebec Ministry of Health and Social Services Website (available in French only).

In the spring of 2010, an outbreak in British Columbia resulted in 82 confirmed cases. Infants and children less than 5 years old were disproportionately affected, as were adults 30 to 39 years old. Where immunization status was known, 59% of cases had not been vaccinated, 29% had received one dose of measles containing vaccine and 12% had received two doses of measles containing vaccine.

In 2008, an outbreak in Ontario began in March and ended in June with a total of 53 confirmed cases. The source of the index case is unknown. About one third of the cases were less than in 10 years old. Where immunization status was known, nearly all cases (29 of 30) had not been vaccinated.

In 2007, an outbreak in Quebec began in April and ended in September with a total of 96 confirmed cases. Although the source of the index case is unknown, the laboratory results suggest that there were two separate importations. Over half (54.7%) of the cases were between the ages of 1 and 10 years. Where immunization status was known, nearly all cases (79 of 86) were in individuals who had not received 2 doses of measles containing vaccine.

Surveillance in Canada

In Canada, surveillance data on measles has been available through Canadian Notifiable Disease Surveillance System (CNDSS). Since 1998, we have had active surveillance conducted through the Canadian Measles/Rubella Surveillance System.   Data from this system is available from 1998 to the present. For further details on each of these systems, please see below:

Canadian Notifiable Disease Surveillance System (CNDSS)

The Canadian Notifiable Disease Surveillance System (CNDSS) is the passive surveillance system coordinated by PHAC which is used to monitor more than 40 nationally notifiable infectious diseases. The objectives of disease surveillance by the CNDSS are to:

1. Facilitate the control of the disease under surveillance by identifying:
   1. Prevailing incidence levels, impacts and trends to assist in the development of feasible objectives for prevention and control of the disease and the evaluation of control programs;
   2. Epidemiologic patterns and risk factors associated with the disease to assist in the development of intervention strategies;
   3. Outbreaks for the purpose of timely investigation and control.
2. Provide information to government agencies, health care professionals, voluntary agencies and the public for information on risk patterns and trends in the occurrence of communicable diseases.

Physicians, hospitals, and/or laboratories report cases of specific diseases to provincial/territorial (P/T) departments of health as mandated by P/T legislation.Notification to the federal level is voluntary. P/T health authorities determine whether the case meets the surveillance case definition and, if so, gather the necessary epidemiologic data on the reported case. Non-nominal data on notifiable cases are submitted to the CNDSS using a “core set” of variables. Data entry and analysis are completed by the Public Health Agency of Canada. Provisional data are published quarterly in the CCDR and finalized numbers of cases and incidence rates are published on-line in annual surveillance summaries.

Canadian Measles/Rubella Surveillance System (CMRSS)

Enhanced case-based surveillance has been conducted by the Centre for Immunization and Respiratory Infectious Diseases since 1998. The system involves weekly reporting by all provinces and territories, including zero-reporting, to PHAC and subsequent weekly reporting by PHAC to the Pan American Health Organization (PAHO). All reported cases are reviewed according to the national case definition prior to their addition to the national database. Probabilistic matching on province/territory (P/Ts), date of birth (or age), sex, onset date, and serogroup (when available) is conducted to retrospectively link epidemiologic and laboratory data for those P/Ts not able to pre-link the data.

Measles Data

The following table contains recent data on the number of confirmed cases and incidence of rubella in Canada from 2005 to 2010.  For previous surveillance data, please see the Notifiable Disease webpage, as well as the Publications section below.

Resources

Case Definitions

Case Definitions for Communicable Diseases under National Surveillance – 2009
Case Definitions for Diseases under National Surveillance -2000

Publications

Measles Surveillance: Guidelines for Laboratory Support. CCDR 1999;25

Guidelines and Recommendations

2006 Canadian Immunization Guide, Measles Vaccine Chapter

2006 Canadian Immunization Guide Table on Vaccines Currently Approved for Use in Canada, March 2008

Guidelines for Control of Measles Outbreaks in Canada. CCDR 1995

Images

Courtesy of Centers for Disease Control and Prevention

Other Resources

PHAC Travel Health Notice - Measles

PAHO Measles Weekly Bulletin