Measles
=======

* Sarah E. Wilson
* Marina I. Salvadori
* Michelle Science

## Canada has had measles elimination status since 1998 but remains vulnerable to outbreaks

Increased measles activity globally raises the risk of travel-related cases in Canada, which can spread rapidly in underimmunized communities.

## Measles is one of the most highly transmissible viral respiratory illnesses

Measles virus is transmitted by respiratory particles (through inhalation or contact with mucous membranes) at short and long range (e.g., airborne), even if airspace is only briefly shared.1 Infection prevention and control measures are critical to prevent spread of the pathogen to susceptible contacts. Health care facilities must be called before patient arrival, and patients should be masked and immediately placed in an airborne isolation room, when available. Staff should don personal protective equipment, including an N95 respirator.2

## Clinicians should consider measles in patients who have travelled, have been exposed to cases, or have compatible clinical presentations

Measles presents with fever, cough, coryza, and nonpurulent conjunctivitis, with a maculopapular rash that starts on the face about 4 days later and spreads down the body. All patients in whom measles is suspected should have a urine test and either a nasopharyngeal or throat swab collected for virus detection by polymerase chain reaction, in addition to diagnostic serology (both immunoglobulin M and G).3

## Ensuring all children are up to date with measles vaccinations is imperative to prevent the return of endemic transmission in Canada

Most measles cases in Canada occur in unvaccinated people, especially children.4 Routine childhood vaccines missed during the COVID-19 pandemic should be caught up urgently. Vaccine coverage of at least 95% with 2 doses of measles-containing vaccine among age-eligible children is required for population immunity. In Canada, the second dose is given at age 18 months or 4–6 years, depending on province and territory.

## Postexposure prophylaxis can reduce the risk of infection or lessen the severity of measles in susceptible contacts

Measles, mumps, and rubella vaccine given to susceptible contacts aged 6 months or older within 72 hours of exposure to a case reduces the risk of developing measles.5 Immune globulin is recommended for susceptible contacts at high risk of complications (infants younger than 12 mo, people who are pregnant or immunocompromised) up to 6 days after exposure.5

## Footnotes

*   Competing interests: Marina Salvadori is an employee of the Public Health Agency of Canada. Sarah Wilson is an employee of Public Health Ontario. No other competing interests were declared.

*   This article has been peer reviewed.

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY-NC-ND 4.0) licence, which permits use, distribution and reproduction in any medium, provided that the original publication is properly cited, the use is noncommercial (i.e., research or educational use), and no modifications or adaptations are made. See: [https://creativecommons.org/licenses/by-nc-nd/4.0/](https://creativecommons.org/licenses/by-nc-nd/4.0/)

## References

1.  Bloch AB, Orenstein WA, Ewing WM, et al. Measles outbreak in a pediatric practice: airborne transmission in an office setting. Pediatrics 1985;75:676–83.
    
    [PubMed](http://www.cmaj.ca/lookup/external-ref?access_num=3982900&link_type=MED&atom=%2Fcmaj%2F196%2F15%2FE524.atom) 
    
    [Web of Science](http://www.cmaj.ca/lookup/external-ref?access_num=A1985AEX7600009&link_type=ISI) 

2.  Interim infection prevention and control recommendations for measles in healthcare settings. Atlanta: Centers for Disease Control and Prevention; updated July 2019:1–12. Available: [https://www.cdc.gov/infectioncontrol/guidelines/measles/index.html](https://www.cdc.gov/infectioncontrol/guidelines/measles/index.html) (accessed 2024 Mar. 23).
    
    

3.  Measles for health professionals. Ottawa: Public Health Agency of Canada; modified 2024 Feb. 27. Available: [https://www.canada.ca/en/public-health/services/diseases/measles/health-professionals-measles.html](https://www.canada.ca/en/public-health/services/diseases/measles/health-professionals-measles.html) (accessed 2024 Mar. 16).
    
    

4.  Coulby C, Reyes Domingo F, Hiebert J, et al. Measles surveillance in Canada, 2019. Can Commun Dis Rep 2021;47:149–60.
    
    

5.  Tunis MC, Salvadori MI, Dubey V, et al.; National Advisory Committee on Immunization (NACI). Updated NACI recommendations for measles post-exposure prophylaxis. Can Commun Dis Rep 2018;44:226–30.