It's the highest number of cases since 1994, according to the Centers for Disease Control and Prevention, and cases have been confirmed in at least 24 states. That's why health officials put out a notice advising global travelers to make sure they're up to date on their measles vaccines.
While no deaths have been reported, 66 people have been hospitalized.
Orthodox Jewish mothers in Rockland County say they have been receiving anti-vaccine conference calls and pamphlets on why parents shouldn't vaccinate their children.
Measles was eliminated in the U.S. in 2000, but "the longer these outbreaks continue, the greater the chance measles will again get a sustained foothold in the United States", the CDC warns.
Health departments are now working to limit exposure there and offer free vaccines to boost the county's immunization rate.
"Many of the cases we have seen have been in travelers who were not vaccinated who went to a country where there's a lot of measles. and brought it back here to California", Pan said.
Measles cases have been reported in 22 states - not Pennsylvania.
It means that the overall vaccination rate over the period was 83.8 per cent, significantly below the 95 per cent the World Health Organisation says is needed to prevent the disease spreading in the community, and leaving a total of 4,928 children without full protection against measles.
The Easter and Anzac period saw a sharp spike in cases across Auckland, from 18 confirmed cases on April 23 to 33 cases on April 30. Virus-laced droplets can hover in still indoor air for up to two hours after someone infected has coughed or sneezed.
The current measles outbreak has many people questioning if they're safe.
"People who live in Orthodox Jewish communities where there is measles-they're the highest risk group right now", she says. "Part of it's the billing, part of it's just a hassle, and part of it is I'm not 100% sold on vaccines", Hostetler said.
In Dudley, it was 1,127 children who had not received their first MMR vaccination by the age of five, and a further 1,613 failed to have the second injection.
The CDC recommends the measles vaccine for anyone over a year old, unless you had the disease as a child.
Measles is a serious, highly infectious disease. The measles vaccine was introduced in 1963, and some early versions of the vaccine were not as effective as those offered today, the CDC says.
15 months, held by her mother, being administered her first dose of mumps, measles and rubella (MMR) vaccine.
"Vaccine preventable diseases belong in the history books, not in our emergency rooms", Azar said.
A highly successful vaccination program caused the number of measles cases to plummet in the USA, but the disease remains endemic in other parts of the world, where it claims tens of thousands of lives annually.
After one dose of the vaccine, it's 93% effective, according to the CDC.
Anyone born before 1957 is considered immune to measles because nearly all individuals born prior to that year likely had measles.
Officials urge adults to confirm their vaccination status by consulting with their doctor.
Nova Scotia doesn't have a publicly accessible vaccination registry, but patient immunization records are usually available through the public health system, or one's personal health-care provider.