Writing in online journal Eurosurveillance, they said recent outbreaks of the disease in the southern regions of Lakonia and East Attica were worrying.

Tackling malaria requires measures such as insecticide spraying, eliminating standing water and tracking mosquito populations as well as people infected with the disease.

"It is clear that surveillance and vector control programs should be strengthened and rapidly intensified," said the study, led by researchers at the Hellenic Centre for Disease Control and Prevention (HCDCP) in Athens.

Greece's healthcare system is under extreme pressure from budget cuts, and experts fear groups such as the poor, unemployed or homeless, many of them immigrants, are not getting treatment they need.

Malaria, which causes high fever and chills and kills hundreds of thousands of people a year worldwide, was once endemic in Greece but was officially eliminated in 1974.

Most cases since then have been imported by travelers, mainly from Africa and Asia.

But Greece has established populations of potentially malarial mosquito species, and last year, 40 cases of locally-acquired malaria were reported, mainly in Lakonia and Attica.

Between January 1 and October 22 this year Greece reported 75 cases in total, 16 of which were locally acquired.

Other mosquito-borne diseases, including West Nile virus carried by Culex modestus mosquitoes, also occur in Greece.

Apostolos Veizis, director of medical-operational support for Medecins Sans Frontieres in Greece, warned in a statement earlier this month that any malaria plan could not work properly unless access to healthcare was available to all.

"It is very important to monitor the situation and invest in mosquito control," he said. "But medically speaking if people cannot be examined and properly diagnosed, it's easy to lose sight of the problem."

The HCDCP experts said a coordinated effort had begun with the collaboration of Greek authorities, the European Centre for Disease Prevention and Control and World Health Organisation (WHO) experts to prevent malaria returning.

(Reporting by Kate Kelland; editing by Andrew Roche)

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