Europe-wide monthly monitoring of measles is to begin after a rise in cross-border transmission and export of cases outside the EU.
In Scotland, twice as many measles cases occurred in the first six months of 2011 as in the whole of 2010, with cases predominately affecting people in their early 20s.
Increased measles activity has been reported across Europe and the European Centre for Disease Prevention and Control (ECDC) has now introduced monthly monitoring of cases.
'There are clear indications that the intensified circulation of measles virus in western Europe over the past few years will continue in 2011,' the centre said in a statement.
It added: 'It is astonishing to see that the EU has become an exporter of measles to the rest of the world, threatening to undermine years of efforts to eliminate endemic transmission of the measles virus.'
The ECDC said it was changing the frequency of its monitoring report from quarterly to monthly 'in order to increase the timeliness of the information provided' to governments and other stakeholders.
Health Protection Scotland (HPS) figures show that in the first six months of 2011, there were 23 laboratory-confirmed measles cases in Scotland, compared with 10 in 2010.
The HPS said that, although overall measles cases were 'not substantially higher' than levels seen in recent years, there had been a shift in the age group affected.
'The median age of cases so far in 2011 is 20.5 years,' it said.
In previous years most cases have been in children under 15.
The ECDC said that, despite measles being preventable by vaccination, European countries were failing to move towards their 2010 goal of eliminating measles transmission by 2015. 'ECDC will step up surveillance and establish a confidential communication platform for timely exchange related to vaccine preventable disease,' it said.