Epidemiology of measles
Measles is extremely infectious and its continued circulation in a community depends on the generation of susceptible hosts by birth of children. In communities which generate insufficient new hosts the disease will die out. This concept was first recognized in measles by Bartlett in 1957, who referred to the minimum number supporting measles as the critical community size (CCS). Analysis of outbreaks in island communities suggested that the CCS for measles is c. 250,000.In 2011, the WHO estimated that there were about 158,000 deaths caused by measles. This is down from 630,000 deaths in 1990. In developed countries, death occurs in 1 to 2 cases out of every 1,000 (0.1% - 0.2%). In populations with high levels of malnutrition and a lack of adequate healthcare, mortality can be as high as 10%. In cases with complications, the rate may rise to 20–30%. Increased immunization has led to an estimated 78% drop in measles deaths among UN member states. This reduction made up 25% of the decline in mortality in children under five during this period.Even in countries where vaccination has been introduced, rates may remain high. In Ireland, vaccination was introduced in 1985. There were 99,903 cases that year. Within two years, the number of cases had fallen to 201, but this fall was not sustained. Measles is a leading cause of vaccine-preventable childhood mortality. Worldwide, the fatality rate has been significantly reduced by a vaccination campaign led 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 WHO. Globally, measles fell 60% from an estimated 873,000 deaths in 1999 to 345,000 in 2005. Estimates for 2008 indicate deaths fell further to 164,000 globally, with 77% of the remaining measles deaths in 2008 occurring within the Southeast Asian region.In 2006–07 there were 12,132 cases in 32 European countries: 85% occurred in five countries: Germany, Italy, Romania, Switzerland and the UK. 80% occurred in children and there were 7 deaths.Five out of six WHO regions have set goals to eliminate measles, and at the 63rd World Health Assembly in May 2010, delegates agreed a global target of a 95% reduction in measles mortality by 2015 from the level seen in 2000, as well as to move towards eventual eradication. However, no specific global target date for eradication has yet been agreed to as of May 2010.On January 22, 2014, the World Health Organization and the Pan American Health Organization declared and certified Colombia free of the measles while becoming the first Latin American country to abolish the infection within its borders.In Vietnam, in the Measles Epidemic in the beginning of 2014, unto April 19 had 8,500 measles cases, 114 fatalities, unto May 30 had 21,639 measles cases, 142 fatalities.