The World Health Organization has issued an urgent warning over measles after an “alarming” 30-fold rise in cases across Europe.

The UN agency reported an enormous increase in numbers affected by the disease, which it said had accelerated in recent months. More than 30,000 cases were reported between January and October last year, compared with 941 cases in the whole of 2022 – a more than 30-fold rise.

Two in five cases were in children between one and four years old. One in five were in people aged 20 and over. The trend is expected to worsen if people do not vaccinate their children against the disease, the WHO said.

The warning came just days after the UK declared a national incident amid a surge in cases, and launched a campaign to encourage parents to get the measles, mumps and rubella (MMR) vaccine for their children.

Dr Hans Kluge, the WHO regional director for Europe, said: “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 (reported in two countries).

“Vaccination is the only way to protect children from this potentially dangerous disease. Urgent vaccination efforts are needed to halt transmission and prevent further spread.”

Measles can lead to serious complications, lifelong disability and death. It can affect the lungs and brain and cause pneumonia, meningitis, blindness and seizures.

“It is vital that all countries are prepared to rapidly detect and timely respond to measles outbreaks, which could endanger progress towards measles elimination,” Kluge added.

The WHO said that falling vaccination rates were to blame, but also that more people were travelling abroad after Covid-19, increasing the risk of cross-border disease transmission and spread within communities.

The WHO Europe region comprises 53 countries, including Russia and some in central Asia, and 40 of those 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 for the first dose of the MMR vaccine, which protects against measles, slipped from 96% in 2019 to 93% in 2022 across Europe. Uptake of the second dose fell from 92% to 91% over the same period.

About 1.8 million infants in the WHO’s Europe region were not vaccinated against measles between 2020 and 2022.

Vaccination rates against measles have been dropping around the world.

In 2022, 83% of children received a first measles vaccine during their first year of life, up from 81% coverage in 2021, but down from 86% before the pandemic, according to the WHO.

In 2021, there were an estimated 128,000 measles deaths worldwide, mostly among undervaccinated or unvaccinated children under five.

In the UK, the head of the UK Health Security Agency (UKHSA) warned last week that the UK was on a “trajectory for everything getting much worse” in the spread of measles.

Prof Dame Jenny Harries said “concerted action” was needed to tackle the virus, and suggested most people were not against their child receiving the MMR jab, but that they needed more information to feel confident about their decision.

She added: “What we are seeing at the moment with measles is that people have forgotten what a serious illness it is … We have had very high vaccination rates, especially for young families, but they are low at the moment.”

Figures released by the UKHSA showed there have been 216 confirmed measles cases and 103 probable cases in the West Midlands since 1 October.

Last week the UKHSA declared a national incident, which it said was an internal mechanism signalling the growing public health risk and enabling it to focus work in specific areas.