Measles: For health professionals
On this page
- What health professionals need to know about measles
- Agent of disease
- Reservoir
- Spectrum of clinical illness
- Transmission
- Disease distribution (global)
- Risk factors
- Prevention and control
- Epidemiology of measles in Canada
- Resources
What health professionals need to know about measles
Measles is a highly infectious disease caused by the measles virus. It is characterized by fever and a maculopapular erythematous rash that begins on the face. It is spread through the respiratory route and can result in serious complications, such as:
- blindness
- deafness
- encephalitis
- severe respiratory infections, such as pneumonia
There is no specific treatment for measles. Measles affects all age groups and can be prevented by immunization. The National Advisory Committee on Immunization (NACI) recommends immunization against measles.
Consult the national case definition for additional information.
Agent of disease
Measles is caused by the measles virus, a member of the genus Morbillivirus of the family Paramyxoviridae.
Reservoir
Humans.
Spectrum of clinical illness
Symptoms of measles begin 7 to 21 days after infection and include:
- prodromal fever
- cough
- coryza
- conjunctivitis
- Koplik spots (white spots on the inner lining of the mouth)
Measles is characterized by a generalized maculopapular rash, which usually appears about 14 days after infection. It lasts 4 to 7 days. It typically begins on the face, advances to the trunk of the body and then to the arms and legs.
Complications such as otitis media and pneumonia occur in about 6% to 7% of reported cases. These complications occur even more commonly in:
- those who are poorly nourished
- those who are chronically ill
- infants less than 1 year of age
Measles encephalitis occurs in approximately 1 of every 1,000 reported cases, and may result in permanent brain damage. Measles infection can cause subacute sclerosing panencephalitis, a rare but fatal disease of the central nervous system. In developed countries, death is estimated to occur in 2 to 3 of every 1,000 cases of measles.
Measles during pregnancy results in a higher risk of:
- premature labour
- spontaneous abortion
- low birth weight
Measles in an immunocompromised person may cause severe symptoms and may have a prolonged course.
Photos of clinical manifestations of measles
Typical red blotchy appearance of measles rash at its peak. The early signs of measles consist of:
- a runny nose with fever
- red and puffy eyes (indicating inflammation of the conjunctiva)
- cough
- malaise
The rash appears fine, flat or slightly raised (macular or maculopapular). It becomes confluent as it progresses, giving it this red, blotchy appearance at its peak. In mild cases, the rash tends not to be confluent. However, in severe cases, the rash is more confluent and the skin may be completely covered.
In individuals with darker skin, the rash may appear granular in the early stage. The slight desquamation or peeling of the skin occurs as the rash clears. It can be seen on the face and upper body of this child.
Transmission
Measles is one of the most highly communicable infectious diseases with greater than 90% secondary attack rates among susceptible persons. The virus is transmitted primarily through the respiratory droplet route (through contact with nasal or throat secretions from infected persons). However, it can also be transmitted through the airborne route (in closed settings, such as a health care setting).
The measles virus can survive at least 2 hours in evaporated droplets and in airborne spread of these fine particles. Transmission in health care settings can even occur when index cases are no longer present. This is due to the persistence of the virus in the air or on environmental surfaces.
The incubation period is about 10 days (ranging from 7 to 18 days). The interval from exposure to appearance of rash averages 14 days. But it can appear as late as 19 to 21 days from exposure.
Cases are infectious from 1 day before the beginning of the prodromal period (usually about 4 days before rash onset) to 4 days after the appearance of rash. People who recover from measles have lifelong immunity to the disease.
Source: Centers for Disease Control and Prevention
Disease distribution (global)
Measles occurs throughout the world and remains a serious and common disease in developing countries. According to the World Health Organization (WHO), measles is a leading cause of vaccine-preventable deaths in children worldwide. The global goal was to reduce mortality due to measles by 95% by 2015 (compared with levels in 2000). This goal was not reached.
By 2017, the global mortality of measles has been reduced by 80%, from 545,000 deaths in 2000 to 110,000 deaths. During this 18 year period, measles vaccination prevented an estimated 21.1 million deaths.
Endemic transmission had ended in the Americas in 2002.The last endemic measles case in the Americas in the post-elimination era was reported in July 2015 in Brazil. The annual count ranged from a low of 85 in 2005 to a high of 1,966 in 2014. Following 2014, the region of the Americas reported 611 cases, 12 cases, and 775 cases in 2015, 2016, and 2017, respectively.
Risk factors
All persons who have not had measles disease or who have not been adequately immunized are at risk of infection. In Canada, adults born before 1970 are generally presumed to have acquired natural immunity to measles. This is due to high levels of measles circulation before that time. Individuals at greatest risk of exposure to measles include:
- travellers
- healthcare workers
- students
Prevention and control
Measles can be prevented with vaccination. The measles-mumps-rubella (MMR) vaccine and/or the measles-mumps-rubella-varicella (MMRV) vaccine are usually given in childhood.
The first dose is recommended at 12 to 15 months of age. A second dose is given at either 18 months of age or any time thereafter, but no later than around school entry. The MMR and MMRV vaccines can also be used in other populations, such as in:
- adolescents
- adults
- specific populations
For more information about vaccination outside childhood, please refer to the online version of the Canadian Immunization Guide.
Any suspected measles case should be reported as soon as possible through local public health channels. Patients should be isolated for 4 days after appearance of the rash in order to prevent transmission of the virus.
All contacts of a suspected measles case should be identified and classified as susceptible or non-susceptible. Susceptible contacts should be managed as per the Guidelines for the Prevention and Control of Measles Outbreaks in Canada.
Epidemiology of measles in Canada
Before the introduction of measles vaccine in 1963 to 1964, measles occurred in cycles with an increasing incidence every 2 to 5 years. At that time, an estimated 300,000 to 400,000 cases occurred annually. Since the introduction of the vaccine, the incidence of measles has declined markedly in Canada (Figure 1).
In 1992, Canada set a goal for measles elimination by 2005 and made great progress towards this goal during the 1990s.
In 1996 to 1997, every Canadian province and territory added a second dose of measles-containing vaccine to its routine immunization schedule. This was done in an effort to reach the goal of measles elimination. Most provinces and territories conducted catch-up programs in school-aged children with measles or measles and rubella vaccine. As a result of high 2-dose vaccine coverage, the last case of measles due to endemic transmission occurred in 1997. Canada achieved measles elimination in 1998.
However, imported cases continue to occur today (Figure 2). Secondary spread from these imported cases tends to be limited. It involves Canadians who are still vulnerable due to inadequate immunization. This includes those who are unimmunized or only have 1 dose of vaccine.
Figure 1. Number of cases and incidence rate (per 1,000,000 population), by year, 1950-2015, and year of vaccine introduction.
Before the introduction of measles vaccine in 1963 to 1964, measles incidence followed a cyclical pattern, with peaks every 2 to 5 years. Since the introduction of vaccine, the incidence has decreased considerably. Further decreases were seen following the introduction of routine 1-dose measles-mumps-rubella vaccine in 1983 and the introduction of routine 2-dose measles-mumps-rubella vaccine in 1996 to 1997 in the provinces and territories.
With routine vaccination, the incidence of measles has declined by over 99% from an average incidence rate of 373.3 cases per 100,000 population in the pre-vaccine era (1950 to 1954) to 0.8 cases per 100,000 population from 2011 to 2015.
Note: In 1963, live vaccine was approved for use in Canada, followed by the approval of killed vaccine in 1964. The killed vaccine had limited availability, and use was discontinued by the end of 1970. A single dose schedule with the live vaccine was introduced into all provincial and territorial routine immunization programs by the early 1970s. The routine 1-dose measles-mumps-rubella vaccine was introduced in 1983 with routine 2-dose measles-mumps-rubella vaccine implemented nationally during 1996-1997. Measles was not nationally notifiable between 1959 and 1968.
Figure 2. Number of imported measles cases, Canada, 1998-2013.
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