Measles cases in England and Wales have risen to 2,016 in 2012 - the highest annual total for 18 years - says the Health Protection Agency.
Merseyside has seen one of the the most prolonged outbreaks of the virus, along with Surrey and Sussex.
More than 860 confirmed cases in England and Wales were in the North West, with around 600 on Merseyside.
Although there were fewer cases recorded in Wirral compared to other parts of the county, the HPA said parents should ensure their children are fully protected against the disease with the MMR vaccine.
Dr Mary Ramsay, head of immunisation at the Agency, said coverage of MMR is now at historically high levels.
"But measles is highly infectious and can spread easily among communities that are poorly vaccinated, and can affect anyone who is susceptible, including toddlers in whom vaccination has been delayed," she said.
The virus can spread through droplets in the air that come out of the nose and mouth when an infected person coughs or sneezes.
Initial symptoms include cold-like symptoms, red eyes which are sensitive to light, a fever and greyish white spots in the mouth and throat.
These become a red-brown spotty rash after a few days.
Dr Ramsay said older children who were not vaccinated at the routine age, who were now teenagers, were at particular risk of becoming exposed while at school.
A regional health authority spokesman said: “The clear message from us is that people need to be vaccinated.
“We are seeing numerous cases in older children, teenagers and adults – and in babies below the age for vaccination.
“We would urge parents of older children, who missed out on vaccination at the appropriate time, to speak to the family doctor and arrange for immunisation now.
“The same applies to teenagers and young adults, even up to the age of 25.
“If you weren’t immunised as a child speak to your family doctor and arrange it now – for your own protection and for the protection of babies and toddlers below the age for vaccination.”
And the spokesman warned: “No-one should dismiss measles lightly. It is rare these day, but people die from measles.”
There were 95 cases in Knowsley 72 in Sefton, while Wirral recorded 17 cases. Liverpool’s total was 31 and there were 35 in Halton and St Helens.