Europe saw 30,000 measles cases last year, 30 times higher than for 2022, the World Health Organization said on Tuesday calling for an "urgent" vaccination campaign.
"We have seen in the region not only a 30-fold increase in measles cases, but also nearly 21,000 hospitalisations and five measles-related deaths. This is concerning," said the organisation.
The WHO Europe region counts 53 countries, including Russia and Central Asia. Forty of the countries registered measles cases in 2023, it said.
Russia and Kazakhstan fared the worst, with 10,000 cases each. In Western Europe, Britain had the most cases with 183.
Vaccination rates against the disease slipped during the Covid-19 pandemic and "urgent vaccination efforts are needed to halt transmission and prevent further spread".
Some 1.8 million infants in the WHO's Europe region were not vaccinated against measles between 2020 and 2022.
"It is vital that all countries are prepared to rapidly detect and timely respond to measles outbreaks, which could endanger progress towards measles elimination."
Vaccination rates against measles have been dropping across the globe.
In 2022, 83 percent of children received a first measles vaccine during their first year of life, up from 81-percent coverage in 2021, but down from 86 percent before the pandemic, WHO has said previously.
In 2021, there were an estimated 128,000 measles deaths worldwide, mostly among under-vaccinated or unvaccinated children under five, it said.