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Measles: For health professionals

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Key information

Measles is a highly infectious disease caused by the measles (rubeola) virus, a member of the Paramyxoviridae family. It is a nationally notifiable disease, characterized by:

  • a prodrome of fever
  • cough
  • conjunctivitis
  • coryza (runny nose)
  • a pathognomonic enanthema (Koplik spots)
  • a maculopapular erythematous rash that:
    • begins on the face
    • spreads to the trunk, arms and legs

The virus is spread through the air and by contact with respiratory secretions from the nose and mouth. It can be prevented with vaccination.

Epidemiology

Humans are the only reservoir for measles.

Incubation period

The incubation period is about 10 days from exposure to the onset of prodromal symptoms (ranging from 7 to 18 days). The interval from infection to appearance of rash averages 14 days, but the rash can appear as late as 19 to 21 days from infection.

Transmission

Measles is one of the most highly communicable infectious diseases with greater than a 90% secondary attack rate among people who are susceptible. The measles virus spreads through the air when a person who is infected breathes, coughs, sneezes or talks. It may also spread through direct contact with fomites or secretions from the nose and throat of a person who is infected.

Airborne precautions should be used for patients with confirmed or suspected measles.

People with confirmed measles are infectious from 4 days before rash onset to 4 days after the appearance of the rash. The measles virus can persist in the air or on surfaces for up to 2 hours after a person who is infected has left the space. People who recover from measles have lifelong immunity to the disease.

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Clinical manifestations

Prodromal symptoms of measles begin 7 to 21 days after infection and include:

  • fever
  • malaise
  • cough
  • coryza (runny nose)
  • conjunctivitis

A pathognomonic enanthema (white spots on the buccal mucosa, known as Koplik spots) may appear 2 to 3 days after symptoms begin.

Measles is characterized by a generalized maculopapular rash, which usually appears about 14 days after infection, or about 3 to 7 days after prodromal symptoms begin. The rash 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

Common complications from measles can include:

  • otitis media (1 of every 10 cases)
  • bronchopneumonia (1 of every 10 cases)
  • diarrhea (less than 1 of every 10 cases)

Complications are more likely in:

  • people who are pregnant
  • those less than 5 years of age
  • people who are immunocompromised

Severe complications of measles can include:

  • respiratory failure
  • encephalitis
    • occurs in approximately 1 of every 1,000 reported cases
    • may result in permanent neurologic sequelae
  • death

Long-term sequelae of measles can include:

  • blindness
  • deafness
  • permanent neurological sequelae
  • subacute sclerosing panencephalitis (SSPE)

SSPE is a rare and fatal degenerative central nervous system disease. It is characterized by:

  • behavioural and intellectual deterioration
  • seizures

These changes occur 7 to 10 years after infection with the measles virus.

SSPE occurs at a rate of 4 to 11 in every 100,000 measles cases, with the highest rates in children infected before 2 years of age.

Measles during pregnancy results in a higher risk of:

  • low birth weight
  • premature labour
  • spontaneous abortion

Images of clinical manifestations of measles

The following images show the typical watery eyes due to conjunctivitis and the red blotchy appearance of a measles rash. The rash usually starts on the face, then progresses to the trunk, arms and legs.

The measles rash appears macular or maculopapular (fine, flat or slightly raised). It becomes confluent as it progresses, giving it a 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.

A slight desquamation or peeling of the skin occurs as the rash clears, which can be more pronounced on darker skin tones.

Koplik spots can classically be seen in the buccal mucosa of the inner mouth, as seen in the fourth image.

Image 1: Measles rash
Figure 1

Courtesy of Dr. CW Leung, Department of Paediatrics and Adolescent Medicine, Princess Margaret Hospital, Hong Kong.

Image 2: Measles rash
Figure 2

Courtesy of the U.S. Centers for Disease Control and Prevention.

Image 1 on the left shows a generalized maculopapular rash on the chest and abdomen of a child.

Image 2 on the right shows desquamation of the skin as the rash clears, which can be more pronounced on darker skin tones.

Image 3: Conjunctivitis
Figure 3

Courtesy of the U.S. Centers for Disease Control and Prevention.

Image 4: Koplik spots
Figure 4

Courtesy of the U.S. Centers for Disease Control and Prevention.

Image 3 on the left shows a child in the later stages of measles rash and the watery eyes due to conjunctivitis.

Image 4 on the right shows the white Koplik spots found classically in the buccal mucosa of the inner mouth.

Risk factors

All persons who have not had a previous measles infection or who have not had 2 doses of a measles-containing vaccine are at risk of measles infection. However, some protection can be provided to young babies as a result of antibody transfer during pregnancy.

In Canada, adults born before 1970 are generally presumed to have acquired immunity due to infection with measles when they were younger. This is due to high levels of measles circulation before 1970. However, vaccination for measles is still recommended for some population groups, even if born before 1970.

The measles chapter in the Canadian Immunization Guide provides:

  • guidance on people who may be considered susceptible or immune to measles
  • subsequent recommendations on need for a measles-containing vaccine

This includes specific recommendations for:

  • health care providers
  • members of the military
  • people planning travel outside of Canada
  • those who attend post-secondary educational settings

These individuals may be more likely to be exposed to measles and could spread measles to large numbers of individuals should they become infected.

Infection is most likely to occur in people who are non-immune travelling to countries where measles is circulating. Occasionally, a returning traveller who is infected with measles can spread infection in Canada. This can be a particular problem if spread occurs in a community where many people are unvaccinated or not fully vaccinated.

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Diagnosis and laboratory testing

Health care providers should suspect measles in a patient presenting with a:

  • febrile illness and rash
  • history suggesting that they are not immune to measles, particularly if they:
    • have travelled
    • are known to have had an epidemiologic link to a measles case or outbreak

Other clinical manifestations, such as the prodrome followed by the rash, the progression of the rash and Koplik spots, raise clinical suspicion for measles.

Health care providers are required to report suspected measles cases to their local public health authority for more direction.

Only those meeting the national case definition are reported to the Canadian Measles and Rubella Surveillance System (CMRSS).

Adequate specimens should be taken in order to diagnose measles and are essential for maintaining adequate viral surveillance. These include:

  • a nasopharyngeal or throat swab for viral detection
  • blood for serology
  • urine for viral detection

Immunoglobulin M (IgM) for measles can be falsely negative if taken less than 3 days after onset of the rash. If results are negative, serology should be repeated 3 or more days after the onset of the rash. In addition, the positive predictive value of IgM testing is reduced due to the low prevalence of measles in the community.

Collection of specimens for viral detection (RT-PCR) is recommended in addition to IgM testing. In addition to confirming the diagnosis in suspect cases, viral detection is used:

  • for genotyping, which can help determine the source of infection
  • to support surveillance that is necessary to monitor measles elimination status

Serological testing may be indicated to confirm the diagnosis of measles or to determine immune status. Serological testing is not recommended to check:

  • susceptibility before measles vaccination
  • response after receiving measles vaccination

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Treatment

There is no specific antiviral treatment for measles infection. Medical management is supportive and aimed at symptom relief and management of complications. This can include rehydration and management of secondary complications of measles, such as bacterial pneumonia.

As vitamin A deficiency is linked to delayed recovery and greater complications with measles, and because measles may precipitate a vitamin A deficiency, health care providers may consider giving vitamin A. The World Health Organization (WHO) recommends children diagnosed with measles be given 2 doses of vitamin A supplements. Dosing information can be found in the WHO position paper.

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Prevention and control

Measles can be prevented with vaccination. The measles-mumps-rubella (MMR) vaccine or the measles-mumps-rubella-varicella (MMRV) vaccine are routinely given in childhood.

The first dose is recommended after the first birthday 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. Two doses provide lifelong immunity in most people.

The MMR vaccine can be given throughout the lifespan in people that have not received all their scheduled vaccinations. The MMRV vaccine is only authorized for individuals 12 months to less than 13 years of age.

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Adverse events and contraindications

Adverse events following immunization with a measles-containing vaccine are usually mild and resolve on their own, including local injection site reactions that occur soon after vaccination. Some side effects may develop 1 to 3 weeks after vaccination, including fever and a mild rash.

Less common, serious adverse events post vaccination can occur.

There are circumstances where measles vaccination may be contraindicated.

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Outbreak control and post-exposure prophylaxis

Health care providers should contact their local public health authority for more direction when a measles case is suspected. Confirmed cases are nationally notifiable. Persons infected with measles should be isolated for 4 days after the appearance of the rash to prevent transmission to others. In health care settings, airborne precautions should be followed, including the use of an airborne isolation room.

All contacts of a person who may be infected with measles 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.

The MMR vaccine or immunoglobulin (Ig) may be used for measles post-exposure management in persons who are susceptible depending on the time since exposure and the risks of the individual who was exposed. Ig provides only short-term protection and requires postponing the administration of MMR vaccine. Long-term protection against measles only follows immunization with MMR or MMRV vaccine, or infection with the measles virus.

Despite the use of MMR vaccine or Ig for post-exposure management, measles infection may occur. Individuals who have been exposed should be counseled regarding:

  • signs and symptoms of measles
  • isolation precautions
  • when to seek medical care, including calling ahead to health care providers to advise them of the possibility of measles before going to a health care setting so that appropriate infection control precautions can be taken

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Surveillance

Measles is a nationally notifiable disease in Canada and measles surveillance is conducted by public health professionals in provinces and territories. Cases meeting the national case definition are reported by health care providers to their local public health authority. Information is subsequently forwarded to provincial or territorial public health officials and then to the Public Health Agency of Canada (PHAC).

National enhanced surveillance of measles is conducted through the Canadian Measles and Rubella Surveillance System (CMRSS). CMRSS is coordinated by PHAC. This system involves weekly collection of enhanced measles data from all provinces and territories, including reporting if there are no cases. This allows for timely surveillance of measles elimination in Canada.

Genotype surveillance is conducted by PHAC's National Microbiology Laboratory (NML) and is included in CMRSS. The NML is a World Health Organization and Pan-American Health Organization accredited measles and rubella regional reference laboratory. Genotyping is an important tool in measles surveillance for 2 key reasons.

  1. It allows for the differentiation between chains of measles transmission, which:
    • is necessary to monitor elimination status
    • can help to determine the source of an infection
  2. It is the only way to distinguish if symptoms are due to recent vaccination or a wild-type measles virus infection.

Weekly summaries of surveillance information collected through CMRSS on measles cases and activity in Canada are provided in the Measles and Rubella Weekly Monitoring Report.

Provinces and territories also submit information on measles cases annually to the Canadian Notifiable Disease Surveillance System.

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History of measles in Canada

Measles has been nationally notifiable since 1924 with the exception of 1959 to 1968. Before vaccinations, about 10,000 to 90,000 people living in Canada were infected with measles every year.

In 1963, a live-attenuated vaccine was approved for use in Canada, followed by the approval of an inactivated vaccine in 1964. The inactivated vaccine had limited availability, and its use was discontinued by the end of 1970.

A single-dose schedule with the live-attenuated vaccine was introduced into all provincial and territorial routine immunization programs by the early 1970s. The routine 1-dose MMR combination vaccine was introduced between 1974 and 1983. The routine 2-dose MMR vaccine was implemented nationally in 1996 to 1997.

In 1996 to 1997, catch-up campaigns were provided to school-aged children to offer them a second dose of a measles-containing vaccine. Since the introduction of the measles vaccine in Canada, measles cases have decreased by more than 99% (Figure 1). Surveillance was interrupted from 1959 to 1968 as per the blue shading.

Figure 1. Number and incidence rates (per 100,000 population) of reported measles cases in Canada by year, 1924 to 2023
Figure 1. Text version below.
Figure 1: Text description
Year Cases Incidence rate (cases per 100,000 population)
1924 39,216 433.6
1925 22,777 247.7
1926 39,429 421.6
1927 28,150 295.2
1928 27,733 284.9
1929 42,132 420.7
1930 21,606 211.9
1931 25,664 247.7
1932 53,508 509.8
1933 13,471 126.9
1934 29,115 271.4
1935 83,127 767.6
1936 55,724 509.6
1937 57,408 520.5
1938 26,328 236.4
1939 44,476 395.3
1940 45,851 403.5
1941 81,051 705.4
1942 26,258 225.6
1943 60,485 513.5
1944 55,317 463.7
1945 26,978 223.8
1946 67,528 550.4
1947 39,455 315.0
1948 66,004 515.7
1949 58,511 435.9
1950 55,653 406.6
1951 61,370 438.8
1952 56,178 389.2
1953 57,871 390.5
1954 36,850 241.5
1955 56,922 363.3
1956 53,986 348.1
1957 49,712 330.3
1958 35,531 229.3
1959 No data No data
1960 No data No data
1961 No data No data
1962 No data No data
1963 No data No data
1964 No data No data
1965 No data No data
1966 No data No data
1967 No data No data
1968 No data No data
1969 11,720 64.4
1970 25,137 136.4
1971 7,439 33.8
1972 3,136 14.1
1973 10,911 48.3
1974 11,985 52.3
1975 13,143 56.6
1976 9,158 38.9
1977 8,832 37.1
1978 5,858 24.4
1979 22,444 92.4
1980 13,864 56.3
1981 2,307 9.3
1982 1,064 4.2
1983 934 3.7
1984 4,086 15.9
1985 2,899 11.2
1986 15,796 60.3
1987 3,065 11.5
1988 710 2.6
1989 21,523 78.5
1990 1,738 6.3
1991 6,151 21.9
1992 2,915 10.2
1993 192 0.7
1994 517 1.8
1995 2,366 8.0
1996 328 1.1
1997 531 1.8
1998 17 0.1
1999 32 0.1
2000 207 0.7
2001 38 0.1
2002 9 <0.1
2003 17 0.1
2004 9 <0.1
2005 8 <0.1
2006 13 <0.1
2007 101 0.3
2008 61 0.2
2009 14 <0.1
2010 99 0.3
2011 752 2.2
2012 10 <0.1
2013 83 0.2
2014 418 1.2
2015 196 0.5
2016 11 <0.1
2017 45 0.1
2018 29 0.1
2019 113 0.3
2020 1 <0.1
2021 0 0
2022 3 <0.1
2023 12 <0.1

In 1998, Canada achieved elimination status for measles with endemic transmission no longer taking place. Most cases arise from outside of Canada with only very limited spread in Canada. Recent trends continue to demonstrate a low overall number of measles cases in Canada (Figure 2).

Measles elimination is a direct result of successful routine vaccination programs.

Figure 2. Number of reported measles cases in Canada since measles elimination, by year, 1998-2023
Figure 2. Text version below.
Figure 2: Text description
Year Cases
1998 17
1999 32
2000 207
2001 38
2002 9
2003 17
2004 9
2005 8
2006 13
2007 101
2008 61
2009 14
2010 99
2011 752
2012 10
2013 83
2014 418
2015 196
2016 11
2017 45
2018 29
2019 113
2020 1
2021 0
2022 3
2023 12

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Why measles outbreaks can happen in Canada

While measles in Canada is no longer considered endemic, outbreaks can happen when a person who is unvaccinated or non-immune travels to a country where measles is circulating and becomes infected with measles and is infectious to others when they return. The risk of measles spreading is highest when there are a lot of unvaccinated or non-immune people clustered together in particular regions or communities. Vaccination rates in Canada, while high, are currently below the necessary threshold for community immunity in some places.

Importation and local transmission can, and has, led to measles outbreaks in Canada.

The vaccination coverage goal of 95% has been established for all recommended childhood vaccines by 2 and 7 years of age based on:

This is especially important for measles-containing vaccines.

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