(CNN) Thirty European nations reported a total of 14,451 measles cases in 2017 -- more than three times the number reported in 2016, according to a new surveillance update from the European Centre for Disease Prevention and Control, an agency of the European Union. There were 4,643 reported cases in 2016.
Measles symptoms include high fever, rash all over the body, stuffy nose and reddened eyes. The virus that causes measles can be transmitted through contact with the secretions of or breathing airborne droplets from an infected person.
Measles is one of the leading causes of death for children, according to the World Health Organization, which estimates that 450 die each day worldwide due to the illness.
The 30 nations surveyed are part of the European Union and/or the European Economic Area. Between January 1 and December 31, 2017, Romania reported the most cases (5,560), followed by Italy (5,004), Greece (967) and Germany (929). These four nations contributed 38%, 35%, 7% and 6%, respectively, of all reported cases.
The total number of measles cases may be an underestimation, particularly in Romania, the ECDC warned. An ongoing outbreak there has caused delays in case-based reporting.
All but two of the EU/European Economic Area countries, Latvia and Malta, reported measles cases for 2017.
Based on laboratory or epidemiological evidence, 27 countries reported the origins of their measles cases in 2017. The status, then, was known for 13,541 cases (94%). Of these, about 89% were classified as endemic (generally found in the area), while 3% were classified as imported, and 9% were import-related.
In 2017, 37% of the people infected with measles were younger than 5 years old, 18% were between 5 and 15, and 45% were 15 or older, the ECDC reported. Children younger than 1 saw the highest incidence, followed by children between the ages of 1 and 4.
The 2017 annual report also looked at vaccination rates among those diagnosed with measles in the EU/EEA nations. Like its US counterpart, the ECDC recommends two doses of MMR vaccine to reach immunity against measles.
Among the total cases, 13,610 (about 94%) had a known vaccination status; of these, 87% had not been vaccinated, 8% had been vaccinated with one dose, and 3% had been vaccinated with two or more doses. Two percent had been vaccinated with an unknown number of doses.
The proportion of unvaccinated cases was highest among children younger than 1 (96%); they are still too young to have received the first dose of the measles vaccine. Meanwhile, unknown vaccination status was highest in adults between the ages of 25 and 29 (13%).
Infants are vulnerable to complications of measles, so they are best protected by herd immunity, the ECDC advises. Herd immunity is achieved when at least 95% of the total population of a country gets the recommended two doses of vaccine.