Measles cases in the United States have now exceeded the highest number on record in a single year since the disease was eliminated in 2000.

Nationwide, at least 673 cases have been reported in 22 states in 2019, according to a tally by The Washington Post of state and local health department data on Wednesday. That's more than the 667 cases reported in 2014, when one large outbreak primarily among unvaccinated people in Amish communities in Ohio accounted for more than half of the total that year.

The Centers for Disease Control and Prevention will provide an official update Monday. The agency is "currently receiving, reviewing, and validating reports of measles cases from state and local health departments," spokesman Jason McDonald said.

CDC's last update was 626 cases from 22 states on April 22.

Video: Despite the massive evidence, the anti-vaccination movement is gaining strength. Scientists are concerned measles could return even though it was 'eliminated' in the U.S. 20 years ago. (Luis Velarde/The Washington Post)

This year, as in the past, the majority of people who have fallen ill were unvaccinated, officials have said. In some communities, anti-immunization activists have spread false claims about the measles, mumps and rubella vaccine, causing concern among parents about inoculating their children. When many people in a community have not been vaccinated, the disease can spread quickly. It is one of the most contagious diseases in the world and can cause serious complications among all age groups, especially young children, adults with weakened immune systems and the elderly.

The states that have reported cases to CDC this year are: Arizona, California, Colorado, Connecticut, Florida, Georgia, Illinois, Indiana, Iowa, Kentucky, Maryland, Massachusetts, Michigan, Missouri, Nevada, New Hampshire, New Jersey, New York, Oregon, Texas, Tennessee and Washington.

The outbreaks are linked to travelers who brought measles back from countries such as Israel, Ukraine and the Philippines, where large measles outbreaks are occurring.

The CDC defines an outbreak as three or more cases. In addition to New York City, there are measles outbreaks in California; Rockland County, New York; New Jersey; and Michigan, where almost all 43 cases are linked to one man who traveled to the Detroit area from Brooklyn, unaware that he had measles.

The largest outbreak is in New York City, centered in a predominantly Orthodox Jewish community in Brooklyn. There have been 334 cases this year, including 31 in just the past week, according to data posted Wednesday. City officials issued summonses to parents of three children last week for failing to have their children vaccinated against measles, a violation of the city's emergency order mandating immunizations to control a surging outbreak.

Among the new outbreaks is one in Los Angeles County, where the health department tweeted Wednesday that it now has five confirmed cases. Los Angeles county health officials said the cases include four confirmed measles cases linked to one another after international travel, and an additional single case of measles after international travel, officials have said.

"We will likely see additional measles cases in Los Angeles County, so it is important if you or someone you know has the symptoms of measles or has been exposed to measles to contact your healthcare provider by phone right away before seeking treatment," said Muntu Davis, Los Angeles County health officer, in a statement Monday.

In Oregon, officials reported an additional four cases in the Portland area. But these cases are not related to the Pacific Northwest outbreak that was centered in nearby Clark County in Washington.

In Washington state, 74 people contracted the infection in that outbreak, including 63 who were unvaccinated. Health officials are expected to declare that outbreak over if no more cases are reported by later this week.

Measles, considered eliminated from the United States in 2000, leads not only to a fever and a rash, it also can cause pneumonia, encephalitis, an inflammation of the brain that can have long-term consequences, and death. Before the widespread use of vaccines began in 1963, it infected millions every year in the United States, killing several hundred.

The CDC recommends children get two doses of the MMR (measles, mumps and rubella) vaccine, starting with the first dose at 12 to 15 months of age and the second dose at 4 to 6 years of age. For adults, if you were born before 1957, the CDC says it is unlikely you need more MMR shots. That's because most people born before then caught measles and thus have natural immunity.

But if someone doesn't have written documentation of an MMR shot, they should talk with their doctor. People born between 1957 and 1989 generally only had one MMR dose. One dose is about 93 percent effective at preventing measles, but anyone in that age group can still get a second dose, health officials say. Two doses are about 97 percent effective. Even if someone has had two doses (or can't remember), doctors say it is okay to get a third dose.

Measles spreads by direct contact with infectious droplets or through the air when an infected person breathes, coughs or sneezes. The virus can remain infectious in the air for up to two hours after an infected person leaves an area. Infected people can spread measles to others from four days before through four days after the appearance of a rash.

This article was written by Lena H. Sun, a reporter for The Washington Post.