This article appeared in the Washington Post. Read the full story here.

The most recent effort to crush the largest measles outbreak in nearly three decades took place at a Brooklyn soccer field.

As Latino players and fans showed up for a weekend tournament, Spanish-speaking health teams offered free vaccines to players and spectators, explaining the outbreak in predominantly Orthodox Jewish communities had spread in recent weeks and had sickened some Latino adults.

“We know there’s a lot of adults who are unvaccinated,” said Paulo Pina, a doctor from NYU Langone Health who was part of the team. “It’s important that we vaccinate them, too, because this is New York: Everybody interacts with everybody.”

New York City’s efforts to halt the largest and longest-lasting measles outbreak in decades have been “nothing short of epic,” said City Health Commissioner Oxiris Barbot. That’s also true of the costs — at least $2.3 million through mid-May, including overtime and purchases for vaccines, supplies and outreach materials. The pace of new cases appears to be slowing at last, but officials still fear the outbreak could reignite at summer camps, through holiday travel to regions experiencing measles outbreaks, and with the start of school.

“All it takes is one 2-year-old slobbering kid” to set off another chain of infection, Barbot said at a recent meeting of her measles outbreak response team.

Around the country, health officials have been trying new strategies to fight misinformation about vaccines and to protect people who aren’t fully vaccinated and are therefore vulnerable to one of the most contagious diseases on Earth.

At least 30 states have reported measles cases, with the total number — 1,164 — constituting the country’s worst outbreak in a quarter century.

A well-organized anti-vaccination movement has driven down immunization rates, especially in isolated communities that have been targeted with misinformation about vaccines.

“The new normal is getting more nuanced in our communication and better understanding these communities that are vaccine-hesitant,” said Michael Fraser, executive director of the Association of State and Territorial Health Officials.

Health officials in some states are analyzing immunization data “down to the school and practice level,” to pinpoint vulnerable areas, Fraser said.

Vermont officials found wide variation among some schools, “creating significant pockets of vulnerability,” Health Commissioner Mark Levine said. State officials have sent memos to school superintendents, principals and headmasters with data for their schools and asked them to follow up with noncompliant families. Adherence to school immunization requirements will be strictly enforced in the fall, officials said.

In Colorado, where childhood immunization rates are among the lowest in the United States, Gov. Jared Polis (D) recently signed an executive order to promote vaccination education. The order requires the state health department to study the cause of low immunization rates and to find new ways to boost vaccinations.

New York City’s outbreak began in October. By this spring, about 400 of the health department’s 6,500 employees were working on the measles emergency. More than 31,000 doses of the measles, mumps and rubella vaccine have been given to individuals in the heart of the outbreak. Since September, at least 642 cases have been reported.

Just outside the city, there have been at least 289 cases in Rockland County, N.Y., including six reported in late July; county officials estimate their costs at more than $2 million.

The measles outbreak in Washington state prompted Gov. Jay Inslee (D) to declare a state of emergency. In Clark County, where all but one of the 72 cases occurred, the public-health staff worked a combined 12,684 hours. The cost to Clark County was $864,679, officials said.

Health department expenses don’t include costs at hospitals. At NYU Langone Health, which treated the largest number of measles cases in New York City, emergency department staff had to be retrained to recognize symptoms after an initial case was misdiagnosed in October. That’s because most staff had never seen measles outside of textbooks, hospital officials said.

Because measles is highly contagious and can stay in the air for up to two hours after an infected person has left a room, hospitals had to scramble to contain the virus.

In late February, after the father of a baby in the neonatal intensive care unit was diagnosed with measles, officials raced to create new screening procedures for its visitors — in one day.

NYU Langone Health admitted 50 patients, most of them children, including 18 who required intensive care. Hospital officials had to buy three special tents that cost $9,000 each to safely transport sick children from the emergency department to hospital rooms. Nearly 80 of about 350 hospital rooms were turned into negative pressure isolation rooms to prevent contaminated air from escaping.

Just one infected person can cause a spike in cases. City officials thought the outbreak was coming to an end earlier this year. In late February, however, 21 measles cases were traced to a child with measles who attended a Williamsburg yeshiva, officials said.

At the city health department headquarters in Long Island City, Queens, several teams make up the 24-hour response. One takes information from health-care providers about suspected cases. Others follow up on the telephone to track where an individual went while contagious. Another group keeps tabs on people with known exposure to measles.

The disease detective work in this outbreak has been unusually hard.

In past measles outbreaks, “we can pinpoint exactly who spread the measles to whom,” said Jennifer Rosen, a senior official working on the response, in an interview. Some community members, however, have not been helpful.

“Either they’re scared and don’t want to answer the phone, or even if they will talk, they’re not necessarily forthcoming about where they went and who they were with while they were infectious,” she said. “So that’s a big challenge.”

At the height of the outbreaks in New York City and Rockland County, health officials did not know where someone became infected in about 70 percent of the cases, according to sources close to the investigation. In mid-July, about 50 percent of city cases had no known or definitive source, a city health department spokesman said.

After the city mandated vaccinations for every person in four Brooklyn Zip codes, parents began taking children to the doctor to get tested for immunity so they could attend school — and those tests revealed to the health department, well after the fact, that many children had been sickened by measles but had never had their illnesses reported.

“At that point, it’s too late for control measures,” Rosen said. “We’ve missed the boat to identify people who were exposed. That’s been a very big challenge during this outbreak, and that’s something that we haven’t experienced before.”

Over 20,000 people were exposed to measles since the outbreak began. Most of them had to be called by the health department, she said.