For health professionals: Measles

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What health professionals need to know about measles

Measles (also known as rubeola and red 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
  • 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.

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 18 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

Source: Government of Canada.

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.

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 90% by 2010 (compared with levels in 2000). This goal was not reached.

By 2010, the global mortality of measles has been reduced by 74%, from 535,300 deaths in 2000 to 139,300 deaths. Both the number of measles cases and deaths continued to decrease through 2012, with a total of 227,245 cases globally and 122,000 deaths.

While measles activity remains endemic in other WHO regions, the virus was eliminated in the region of the Americas in 2002. The last endemic measles case occurred 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, the Americas reported the highest number of measles cases since the virus was eliminated (a total of 1255 cases). The majority were associated with a large outbreak in Quebec, Canada. Following this outbreak, the region of the Americas reported 135 cases in 2012 and 422 cases in 2013.

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 to destinations outside of the region of the Americas
  • health care workers
  • students

Prevention and control

Measles can be prevented by immunization. Immunization of all children is recommended at 12 to 15 months of age as part of a combined vaccine. This combined vaccine contains measles, mumps and rubella (MMR) or measles, mumps, rubella and varicella (MMRV). A second dose is given at either 18 months or at 4 to 6 years of age. The MMR and MMRV vaccines can also be used in other populations, such as in:

  • adolescents
  • adults
  • special 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
Figure 1. Number of cases and incidence rate (per 1,000,000 population), by year, 1924-2013, 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. The incidence rate decreased from 3,700 cases per 1,000,000 population from 1924 to 1958 to 2.7 cases per 1,000,000 population from 1998 to 2013. Note: measles was not nationally notifiable between 1959 and 1968.

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
Figure 2. Number of imported measles cases, Canada, 1998-2013.

From 1998 to 2013 there were a total of 134 imported measles cases (5 in 1998; 9 in 1999; 10 in 2000; 11 in 2001; 4 in 2002; 9 in 2003; 5 in 2004; 3 in 2005; 5 in 2006; 5 in 2007; 6 in 2008; 4 in 2009; 10 in 2010; 29 in 2011; 7 in 2012; and 12 in 2013). The distribution ranged from a minimum of 3 importations in 2005 to a maximum of 29 importations in 2011. The median number of importations per year was 6.5.

Measles surveillance in Canada

Health professionals in Canada play a critical role in identifying and reporting cases of measles. See the surveillance of measles section for more information on surveillance in Canada.

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