This escalates a long-simmering feud between Bill de Blasio and New York City’s health department. The mayor has tried to cut out and work around their expertise at times, which created a number of headaches for all involved. Now the top executive at the department has abruptly resigned — and made sure everyone knows why:

New York City’s health commissioner, Dr. Oxiris Barbot, resigned on Tuesday in protest over her “deep disappointment” with Mayor Bill de Blasio’s handling of the coronavirus outbreak and subsequent efforts to keep it in check.

Her departure came after escalating tensions between City Hall and top Health Department officials, which began at the start of the city’s outbreak in March, burst into public view.

“I leave my post today with deep disappointment that during the most critical public health crisis in our lifetime, that the Health Department’s incomparable disease control expertise was not used to the degree it could have been,” she said in her resignation email sent to Mr. de Blasio, a copy of which was shared with The New York Times.

“Our experts are world renowned for their epidemiology, surveillance and response work. The city would be well served by having them at the strategic center of the response not in the background.”

De Blasio had moved contact tracing away from Barbot’s control, which apparently was the last straw:

Barbot’s resignation comes after de Blasio stripped control of the city’s COVID-19 contact tracing program from the health department, which has historically handled tracing. The mayor instead placed the program under Health and Hospitals, the agency that runs the city’s public hospitals.

In recent weeks, the city’s contract tracing program has come under fire after complaints from contact tracers about the program being disorganized and having poor working conditions.

Barbot also butted heads with NYPD Police Chief Terence Monahan when he asked for more face masks for his officers in March, according to the New York Post. Following the incident, which was widely reported in the media, Barbot disappeared from public view for days — at the height of the coronavirus outbreak in New York City.

The city’s performance hasn’t exactly covered the Big Apple in glory, but Barbot’s resignation punctures the narrative that de Blasio and Andrew Cuomo have tried to inflate over the last few weeks. Both have insisted that New York and NYC have led the way in dealing with COVID-19, a rather ridiculous assertion given the massive number of deaths, especially in nursing homes. Reporters had finally started taking an interest in poking around that issue, and Barbot’s resignation makes it even more acute.

Here’s de Blasio trying to put a good face on it by claiming to be world-beaters at pandemic management:

Note well that de Blasio never even mentions Barbot, let alone thank her for her contributions. If NYC was really that good at managing the pandemic, then Barbot had to be one of the key people. And if she’s not even worth mentioning in the same breath, then it makes de Blasio’s bloviating even more transparently nonsensical.

At some point, de Blasio is going to have to explain that conundrum. Perhaps Barbot will have more to say — hopefully soon, too.