In England – London, the South East, West Midlands and the South West regions have reported the most cases.
About half of the cases in England in 2018 have been in people over 15 years of age.
Dr Yvonne Doyle, London regional director for Public Health England, said: “We are seeing a concerning increase in measles cases across London which could lead to a wider outbreak in unvaccinated children and adults.
“Those who have not received two doses of the vaccine in the past — or who are unsure — should speak to their GP.
“There’s no harm in receiving an additional dose where there is any uncertainty.
“It’s crucial pregnant women have been vaccinated with MMR, as rubella in particular can cause serious complications during pregnancy.”