At least 30 people from the Dutch Bible belt have so far been diagnosed with measles in the first outbreak of the sometimes fatal disease in 13 years.
The infections are largely based around strict Protestant schools in a broad sweep across the country from the Veluwe area to Zeeland province, the public health institute RIVM said in a statement.
Fundamentalist Protestants in the Netherlands do not believe in having their children vaccinated. The measles vaccine is given to most children in the BMR combination injection at the age of 14 months and again at nine years.
The total number of cases may be far higher than 30 because not everyone will have visited their doctor, the RIVM said. Measles is spread by coughing and sneezing.
The RIVM said it is monitoring developments closely and expects the spread of the disease to widen among unvaccinated children. Parents can visit their doctor for a catch-up injection, the RIVM said.
The last measles outbreak in the Netherlands was between 1999 and 2000 when there were some 3,300 infections and three children died.