Measles epidemiology and demographics

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Guillermo Rodriguez Nava, M.D. [2]

Overview

According to the World Health Organization (WHO), measles is a leading cause of vaccine preventable childhood mortality. Worldwide, the fatality rate has been significantly reduced by partners in the Measles Initiative: the American Red Cross, the United States Centers for Disease Control and Prevention (CDC), the United Nations Foundation, UNICEF and the World Health Organization (WHO). Globally, measles deaths are down 60 percent, from an estimated 873,000 deaths in 1999 to 345,000 in 2005. Africa has seen the most success, with annual measles deaths falling by 75 percent in just 5 years, from an estimated 506,000 to 126,000.

Epidemiology and Demographics

Developed Countries

  • In developed countries, most children are immunized against measles at the age of 18 months, generally as part of a three-part MMR vaccine (measles, mumps, and rubella).
  • In the 1990s, the governments of the Americas, along with the Pan American Health Organization, launched a plan to eradicate Measles, Mumps, and Rubella from the region.
  • Indigenous measles has been eliminated in North, Central, and South America; the last endemic case in the region was reported on November 12, 2002.[1]
  • Most recently, in 2007, the country Japan has become a nidus for the Measles. Japan has suffered a record number of cases, and a number of universities and other institutions in the country have closed in an attempt to contain the outbreak.
  • Outbreaks are still occurring, however, following importations of measles viruses from other world regions.
  • While some smaller organizations have proposed a global MMR eradication, none is likely to take place until, at least, after the worldwide eradication of Poliomyelitis.

United States of America

Pre-elimination Era

  • In the decade prior to the licensure of live measles vaccine in 1963, an average of 549,000 measles cases and 495 measles deaths were reported annually.[2]
  • Almost every American was affected by measles during their lifetime; it is estimated that 3–4 million measles cases occurred each year.
  • Following implementation of the one dose measles vaccine program, there was significant reduction in the reported incidence in the United States by 1988 resulting in decline in measles-related hospitalizations and death.
  • During 1989–1991, a resurgence of measles occurred when over 55,000 cases and 123 deaths were reported.
  • The epidemiology during the resurgence was characterized mainly by cases in unvaccinated preschool-age children who had not been vaccinated on time with one dose of measles vaccine.
  • Outbreaks were reported among highly vaccinated school-age children who received one dose of measles-containing vaccine.
  • In 1989, a second-dose vaccination schedule was recommended by the Advisory Committee on Immunization Practices (ACIP), the American Academy of Pediatrics (AAP), and the American Academy of Family Physicians (AAFP).
  • In 1998, the ACIP recommended that states ensure second dose coverage of children in all grades by 2001.
  • Following the resurgence, improved implementation of the timely administration of the first dose of MMR vaccine and increased implementation of two doses among school-age children led to a dramatic decline in measles cases.
  • In 2000, endemic measles was declared “eliminated” from the United States.

Post-elimination Era

  • During 2001–2011, 911 measles cases were reported. [2]
  • The median number of measles cases reported per year was 62 (range: 37–220 cases/year).
  • Measles incidence has continuously remained below one case per million since 1997. The majority of measles cases were unvaccinated (65%) or had unknown vaccination status (20%).
  • Of the 911 reported measles cases, 372 (40%) were importations (on average 34 importations/year), 239 (26%) were epidemiologically linked to these importations, 190 (21%) either had virologic evidence of importation or had been linked to those cases with virologic evidence of importation, and 110 (12%) had unknown source (unknown source cases represent cases where epidemiologic- or virologic-link to an imported case was not detected0
  • The highest incidence of measles cases in recent years occurred in 2008 (0.48 cases/million) and 2011 (0.72 cases/million):
    • The epidemiology of measles in 2008 was characterized by (1) a high proportion (95%) of cases among U.S. residents who were unvaccinated or who had unknown vaccination status, most of whom were U.S. school-age children whose parents had religious or philosophical objections to vaccination, and (2) more spread from imported cases than other years.
    • In 2011, 220 measles cases were reported, the highest number of reported measles cases since 1996; 80 (36%) were importations, 144 (65%) were unvaccinated, and 47 (21%) had unknown vaccination status. Most of the importations were the result of unvaccinated U.S. travelers who had traveled to measles endemic countries, mainly Western Europe and India.
  • Although measles elimination has been achieved in the United States, importation of measles will continue to occur as measles remains endemic in many other parts of the world.
  • Current measles epidemiology in the United States is determined by characteristics of the imported case and their susceptible contacts.

Measles Outbreaks in the United States in the Post-elimination Era

Measles Cases and Outbreaks. Image extracted from CDC Measles Cases and Outbreaks.[3]
  • From 2001 through 2011, 63 outbreaks of measles were reported; they were small with a median of six cases (range: 3–34).[2]
  • The outbreaks mostly involved individuals who were exposed to imported measles cases or were infected during a resulting chain of transmission and who were either unvaccinated or had unknown vaccine status.
  • Lack of adherence to existing recommendations for measles prevention among groups at high risk (for example, individuals who travel internationally), can spread measles to susceptible populations, including infants too young to be vaccinated and groups who routinely oppose vaccination.
  • The size of the outbreaks was limited due to immediate control measures, high population immunity, and high measles vaccine effectiveness.
  • The settings, when known, included households, educational facilities (e.g., schools, day care), churches, health care, homeless shelters, and congregate settings.
  • Traveling to measles endemic regions was also commonly reported.
  • The most commonly reported setting in 2011 was associated with household.
  • In 2005, there was an outbreak in a non-immunized population in Indiana and Illinois, transmitted by an Indiana girl who visited Romania without being vaccinated.
  • In June 2006, there was an outbreak in Boston which resulted from a resident who had recently visited India.[4]
  • Responding to measles cases and outbreaks is time consuming and costly for state health departments.
  • An outbreak in San Diego in 2008 cost the public health department $124,517 to contain, with additional medical costs and costs incurred by families for quarantining unvaccinated contacts at home. Total outbreak costs were $176,980.
  • Another outbreak in 2008 affecting several hospitals cost about $800,000 to contain, more than $100,000 per case.
  • In January–May 20, 2011, more than 30 countries in the WHO European Region reported an increase in measles, and France was experiencing a large outbreak. Most of the cases that were brought to the U.S. in 2011 came from France.
  • In January 1-August 24, 2013, the U.S. experienced 11 outbreaks, three of which had more than 20 cases, including an outbreak with 58 cases.
  • This year (2014) the United States is experiencing a record number of measles cases. From January 1 to June 20, 2014, there have been 514 confirmed measles cases reported to CDC's National Center for Immunization and Respiratory Diseases (NCIRD). This is the highest number of cases since measles elimination was documented in the U.S. in 2000.
  • The majority of the people who got measles are unvaccinated.
  • Measles is still common in many parts of the world including some countries in Europe, Asia, the Pacific, and Africa, travelers with measles continue to bring the disease into the U.S.
  • Measles can spread when it reaches a community in the U.S. where groups of people are unvaccinated.

South America

  • There are also plans underway to eliminate Rubella from the region by 2010.[1] As of 2006, endemic cases were still being reported in Bolivia, Brazil, Colombia, Guatemala, Mexico, Peru, and Venezuela, they are currently vaccinating Dominican Republic.

Developing Countries

  • In developing countries, measles remains common. Unvaccinated populations are at risk for the disease.
  • After vaccination rates dropped in northern Nigeria in the early 2000s due to religious and political objections, the number of cases rose significantly, and hundreds of children died.[5]
  • A 2005 measles outbreak in Indiana was attributed to children whose parents refused vaccination.[6]
  • In the early 2000s the MMR vaccine controversy in the United Kingdom regarding a potential link between the combined MMR vaccine (vaccinating children from mumps, measles and rubella) and autism prompted a comeback in the measles party, where parents deliberately infect the child with measles to build up the child's immunity without an injection. This practice poses many health risks to the child, and has been discouraged by the public health authorities.[7] Scientific evidence provides no support for the hypothesis that MMR plays a role in causing autism.[8] Declining immunization rates in the UK are the probable cause of a significant increase of cases of measles, 2006 being the highest on record, and 2007 already showing an increase on the previous year.[9]

References

  1. 1.0 1.1 www.paho.org. Retrieved on 2013-02-25.
  2. 2.0 2.1 2.2 Measles.
  3. Measles Cases and Outbreaks.
  4. Boston Globe article, NPR report.
  5. "Measles kills more than 500 children so far in 2005", IRIN, 2005-03-21. Retrieved on 2007-08-13. 
  6. Parker A, Staggs W, Dayan G et al. (2006). "Implications of a 2005 measles outbreak in Indiana for sustained elimination of measles in the United States". N Engl J Med 355 (5): 447–55. PMID 16885548.
  7. Dillner L. "The return of the measles party", Guardian, 2001-07-26. Retrieved on 2007-08-13. 
  8. Rutter M (2005). "Incidence of autism spectrum disorders: changes over time and their meaning". Acta Paediatr 94 (1): 2–15. PMID 15858952.
  9. Telegraph article on increasing cases of measles

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