A whopping 314 reported cases of measles have been confirmed as of March 21 compared to 374 cases confirmed in all of 2018, according to the CDC.
Health officials in New York City have reported 181 cases there as of Wednesday, while Washington state has seen 74 cases as of Friday.
Much of the measles cases in New York have been concentrated among children of Orthodox Jewish families, many of whom attend religious schools where the vaccination rates are below 95 percent, which is the threshold considered necessary to maintain immunity among the community, known as herd immunity, according to Kaiser Health News.
An outbreak in Texas has resulted in 14 confirmed cases as of Thursday, and the state of Illinois has reported six cases in 2019 so far.
A new bill in California, where seven cases of measles have been confirmed in 2019, would require every vaccination exemption for school-age children to be approved by the state Department of Health, the San Francisco Chronicle reported.
In addition, the CDC has confirmed measles cases in Arizona, Colorado, Connecticut, Georgia, Kentucky, Michigan, Missouri, New Hampshire, New Jersey and Oregon.
Measles cases have increased in recent years in part because of fears fanned by anti-vaccine activists, according to Kaiser Health News.
Before people began being vaccinated in the early 1960s, four million people were infected every year, win about 50,000 hospitalizations and 500 deaths annually, Kaiser Health News reported. The measles vaccine is 97 percent effective, according to health officials.
ABC News' Darren Reynolds contributed to this report.