Measles outbreaks have killed at least 37 people in the European region so far this year, the European branch of the World Health Organization warned Monday.

The health agency said more than 41,000 children and adults were infected with the highly contagious disease between January and June — well above the number of total cases in any other year over the past decade.

Read more: WHO 'taken aback' by high number of measles cases

"We are seeing a dramatic increase in infections and extended outbreaks," Zsuzsanna Jakab, WHO regional director for Europe, said in a statement.

"We call on all countries to immediately implement broad, context-appropriate measures to stop further spread of this disease. Good health for all starts with immunization."

Read more: Measles infection rate triples in Germany

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What is behind the increase?

The Copenhagen-based body said a main reason for the surge in infections was a drop in routine immunization coverage among marginalized groups in some countries.

France, Georgia, Greece, Italy, Russia, Serbia, and Ukraine all recorded more than 1,000 measles cases in the first half of 2018. Ukraine was hardest-hit, with 23,000 infections. The most fatalities were reported in Serbia, where 14 people died.

Read more: UN health body calls for closing the immunization gap

The measles virus can spread quickly by coughing, sneezing or personal contact with infected nose or throat secretions.

The WHO said preventing outbreaks required at least 95 percent coverage with two doses of vaccine every year in every community.

Between 2010 and 2017, the highest annual total for measles cases was 23,927 in 2017. The lowest was 5273 in 2016.

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