Academic journal article Bulletin of the World Health Organization

Elimination of Endemic Measles Transmission in Australia/Elimination De la Transmission Endemique De la Rougeole En Australie/Eliminacion De la Transmision Endemica del Sarampion En Australia

Academic journal article Bulletin of the World Health Organization

Elimination of Endemic Measles Transmission in Australia/Elimination De la Transmission Endemique De la Rougeole En Australie/Eliminacion De la Transmision Endemica del Sarampion En Australia

Article excerpt

Defining elimination

Several WHO regions have set target dates for the elimination of the transmission of endemic measles. The WHO Regional Office for the Western Pacific (WPRO) has nominated the target date of 2012. (1) Since measles elimination was first proposed, definitions of elimination have progressed from requiring a reduction to zero in the incidence of infection in a defined geographical area, (2) to the absence of endemic measles transmission and the lack of sustained transmission following an importation of measles virus in a large and well populated geographical area, as outlined in guidelines by WPRO. (3) The indicators adopted by WPRO to monitor the progress towards measles elimination provide an operational definition of measles elimination. (3,4)

Papania & Orenstein have argued that elimination can be declared if multiple lines of evidence demonstrate the absence of endemic measles transmission. (5) Several countries have declared elimination of endemic measles transmission using criteria that have become more rigorous over time (summarized in Table 1, available at: http://www.who.int/bulletin/ volumes/87/1/07-046375/en/index.html), including the criteria we use here to declare elimination in Australia.

As with other countries that have declared elimination of measles, Australia's national elimination plan included high two-dose immunization coverage and a disease surveillance system capable of a rapid response to potential measles outbreaks. (16) Australia, like many other countries that have declared elimination, would have difficulty meeting the WPRO elimination criteria based on currently available reporting of the investigation of presumptive measles cases (Table 2, available at: http://www.who.int/bulletin/volumes/87/1/07-046375/en/ index.html). However we believe multiple lines of evidence conclusively demonstrate the elimination of endemic measles transmission from Australia since 2005 at the latest, when notified confirmed cases were < 1 per million population. In this paper we outline how these criteria have been met, compare them with the WPRO criteria and justify their validity. We argue that a broader range of internationally accepted criteria for measles elimination is warranted.

Evidence of elimination

Low incidence

Notifications of measles cases in Australia were sporadic until the establishment of the National Notifiable Diseases Surveillance System (NNDSS) in 1991. (17) Since then, public health legislation in all jurisdictions has included the mandatory reporting of measles cases by laboratories, clinicians and hospitals, to state and territory health departments. Notifications of confirmed cases are forwarded to the NNDSS. Since 2004, all Australian states and territories have adopted a case definition for a confirmed case of measles that requires laboratory evidence from an approved reference laboratory of an epidemiological link to a laboratory-confirmed case in conjunction with clinical evidence. (18) These improvements mean that all confirmed measles cases notified to the NNDSS since 2004 are likely to represent true cases (WPRO criterion 1, Table 2).

Since a large national outbreak in 1993-4 (Box 1), there has been a progressive downward trend in measles notifications. The 10 confirmed cases of measles in 2005 (0.5 cases per million population) was the lowest annual figure ever reported on the NNDSS (Fig. 1). (24) A total of 125 cases were reported in 2006 (6 cases per million). (24) However, a large proportion (~54%) was attributable to a nationwide outbreak linked to the tour of a foreign spiritual group. Attendees at tour meetings were disproportionately opposed to vaccination and transmission was predominantly confined to one generation. (25,26) In 2007, 11 cases were reported to the NNDSS (0.5 cases per million (24)). In both 2005 and 2007, Australia met the WPRO target of 1 case per million population but not in 2006, a year in which we believe that endemic measles transmission did not occur in Australia. …

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