Although the absence of locally acquired measles cases within a country with sensitive surveillance is a wonderful aspiration, this is generally only achieved by countries that are isolated

or remote and having few international travel movements selleck chemicals to and from measles-endemic countries. Mongolia and many remote island countries in the Western Pacific have enjoyed this experience for a number of years [18]. However, while measles is endemic anywhere in the world and the current scale of international travel is maintained, the integrity of most countries’ population immunity will be regularly tested by importation of measles virus in non-immune residents returning from endemic areas or infectious visitors from endemic areas. An indicative incidence

rate was nominated by the WHO as a milestone towards achieving elimination. This was set at less than one laboratory or epidemiologically confirmed measles case per million population annually; excluding imported cases [19]. However, once a country succeeds in eliminating measles, this indicator is no longer helpful. For Ibrutinib in vitro countries with relatively large numbers of visitors and local international travellers compared to their population denominator, for example Australia and countries of the Caribbean, despite interrupting endemic measles transmission this indicator may still be regularly exceeded because of multiple short chains of local transmission following importations [20]. In that situation, the classification of cases as imported or import-related (for onward transmission) is the key to documenting that elimination is being sustained. If chains of transmission extend beyond 12 months, then measles is by definition no longer eliminated. Of much greater value than incidence is the early detection CYTH4 and careful categorisation of all measles cases by their source of infection; “imported”, “import-related”, “endemic” or “unknown” [19] and [21]. Ideally 80% or more of all confirmed measles cases should be “imported” or “import-related”. In the Western

Pacific, this was achieved by the three countries with measles activity that were recently verified as having interrupted endemic measles transmission; Australia, Macao (Special Administrative Region of China), and the Republic of Korea. The fourth country Mongolia had experienced no measles cases for a four year period and had consistently detected and investigated an adequate number of rash and fever cases to exclude measles. This vouched for the sensitivity of their surveillance. The ability to categorise measles source for the majority of cases reflects the thoroughness and timeliness of epidemiological investigation, including the submission of appropriate specimens to permit laboratory confirmation of cases, while simultaneously revealing the integrity of herd immunity.