There were more new cases of measles reported last week in the United States than in any other week of 2019, new government data shows, with the outbreak spreading to four states that recorded their first cases of the virus for the year.
In the first week of April, the country added 78 new measles cases, according to the Centers for Disease Control and Prevention, with Florida, Indiana, Massachusetts and Nevada confirming their first patients. Two weeks ago, the country added 73 new cases, which was the most for the year until last week.
The dozens of new infections take the count to 465 confirmed cases this year, the second-greatest number of reported cases in a year since 2000, when measles was declared eliminated in the United States.
At the current rate, the country would surpass by midyear the number of measles cases in 2014, when an outbreak among unvaccinated Amish communities in Ohio helped drive the total to667 reported cases, the high mark for this century.
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Fifteen other states have also reported cases this year: Arizona, California, Colorado, Connecticut, Georgia, Indiana, Kentucky, Michigan, Missouri, New Hampshire, New Jersey, New York, Oregon, Texas and Washington.
In Brooklyn, a large outbreak in the Orthodox Jewish community prompted New York City todeclare a public health emergencyon Tuesday. Mayor Bill de Blasio said that the city would require unvaccinated people living in select ZIP codes in the Williamsburg neighborhood to receive the measles vaccine.
The largest outbreak has been in the northern suburbs of New York City, with 167 cases in Rockland County as of Friday.
A judge thereput a hold last weekon a county order that had barred children and teenagers who were not vaccinated against measles from public places. Public health experts said that they could not recall any action like what the county tried to do in recent years.
Rockland County is home to a large ultra-Orthodox Jewish community where there has been some resistance to vaccinations. The outbreakhas been tracedto an annual Hasidic pilgrimage from Israel to Ukraine. The vast majority of states allow families to opt out of getting vaccinated if they object on religious grounds.
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Most of the American cases since 2000 have been the result of people traveling to or from countries where measles is endemic because there is little vaccination.
In the United States, measles immunization is stable and high — more than 90 percent of children — according to C.D.C.tracking, but there are a small number of people in scattered pockets who remain unvaccinated.
Last week, the University of California, Davis,sent lettersto about 200 people warning them that they and anyone who had accompanied them to a Sacramento emergency room on March 17 had encountered a “possible exposure” to the measles virus. A young girl who is believed to have contracted the virus on an overseas trip had visited the U.C. Davis Medical Center that day.
Officials did not realize that the girl, who was unvaccinated, had the measles until two days after she visited the hospital. The girl was from Calaveras County, southeast of Sacramento.