Measles is a highly contagious airborne disease which spreads easily through coughs and sneezes. Initial symptoms usually include a fever, cough, runny nose and inflamed eyes. A red rash appears on the face and body a few days later. Measles can sometimes lead to serious health complications, including infections of the lungs and brain. Measles can be very dangerous for small children and babies. Bronchopneumonia from measles complications can be deadly.
While vaccination rates are improving, the WHO says coverage is not high enough to prevent circulation of the virus in many countries.
Ukraine reported the highest number of measles cases last year - more than 10 times that of the next highest, Serbia. Vaccination rates for measles, mumps and rubella in Ukraine fell sharply over a number of years during its conflict with Russia, reaching 31% in 2016 - among the lowest in the world.
Over 90% of cases were in 10 countries, including France, Italy and Greece.
There were 72 deaths from measles in Europe in 2018 compared with 42 in 2017.
Authorities in the Philippines have declared an outbreak of the highly contagious measles virus in several areas including the capital, Manila.
As of 26 January there have been 1,813 measles cases and 26 deaths, according to the Department of Health Epidemiology Bureau. That is a 74% increase from 2018.
There is now increasing concern for the 2.4 million unvaccinated children. Parents have been reluctant to have their children immunised at government health centres, after complications related to a dengue vaccine, Dengvaxia.
Dr Gundo Weiler, World Health Organisation (WHO) representative to the Philippines, said immunisation rates were well below the target of 95% and decreasing.
In 2016 the rate was about 75%, but fell to 60% in 2017 and has likely fallen further in 2018.