Mayor Bill de Blasio did look a little ridiculous with a bandana covering half his face Tuesday but, hey, what’s new? He has always been Mayor Putz.

In his own small way, he is trying to do the right thing and lead by example as his city is ravaged by the coronavirus. For that he ­deserves a pat on the back.

We all should be wearing masks out in public. It is a commonsense courtesy to protect others as well as ourselves. It is a tangible reminder not to drop your guard against an invisible killer.

It stops you touching your face and warns people that you might be contagious. Which you might be, even if you feel hale and hearty, because Asian data show that up to a third of COVID-19 spreaders have no symptoms.

So kudos to any public figure willing to sacrifice pride and don a mask, even one that looks like it came out of his wife’s underwear drawer.

It’s difficult enough to overcome the social stigma of facial coverings in western countries but vacillating advice from major health organizations has only left people confused.

Last week, the Centers for Disease Control and Prevention reversed its position and recommended that Americans wear masks after all, even if asymptomatic.

On Monday, the World Health Organization, as if it hasn’t caused enough trouble, decided to contradict the CDC.

“Masks alone cannot stop the #COVID19 pandemic,” WHO said in a flurry of 12 tweets.

“What is clear is that there is limited research in this area.”

Then it pumped out a confusing, five-page paper claiming: “There is currently no evidence that wearing a mask . . . by healthy persons in the wider community setting . . . can prevent them from infection.”

But that flies in the face of a study from Singapore, cited by the CDC, that healthy people can spread the virus without symptoms. N95 masks needed by health workers are in short supply but even homemade cloth masks are better than nothing.

The unhelpful mask conflict is typical of the toxic pointlessness of WHO. It is worse than useless. It is what it accuses masks of being: a costly distraction that lulls you into a false sense of security.

What’s it been doing in the 17 years since the last deadly respiratory virus, SARS, emerged from China?

WHO was wrong about ­COVID-19 from the start. It bought China’s lies and then praised its “transparency.”

Taiwan warned Dec. 31 that the virus was contagious. Two weeks later, as China was punishing doctors and destroying virus samples, WHO tweeted the Chinese line that there was “no clear evidence of human-to-human transmission.”

It wasn’t until March 11, after the virus had taken hold around the world, that WHO declared a pandemic.

No wonder the president finally directed his ire this week at WHO, a United Nations agency, and threatened to cut its US funding for failing to warn the world about the disaster brewing in Wuhan.

“They [WHO] seem to be very China-centric,” he said. “They err on the side of China. They called it wrong. They could have called it months earlier . . . They should have known.”

WHO Director-General Tedros Adhanom Ghebreyesus responded Wednesday with a threat: “If you don’t want many more body bags you refrain from politicizing it.”

Really? This is Mafia talk.

Not once has Tedros criticized China’s malfeasance, including the hoarding of medical supplies, which caused shortages of protective gear, especially the masks WHO tells us we don’t need.

The single most effective measure taken in this country to slow the infiltration of the virus was made against Tedros’ vehement opposition: the president’s China-flight ban on Jan. 3, for which he was slammed as a xenophobe.

After the ban, Tedros tweeted: “The greatest enemy we face is not the virus itself; it’s the stigma that turns us against each other.”

It’s not stigma sending Americans to hospital gasping for breath. It’s not stigma piling up bodies in refrigerated trucks in Brooklyn.

We must never again trust woke transnational bureaucracies.

Instead, we should follow de Blasio’s lead and wear any mask we can find. If WHO is against them, it’s a fair bet they’re worthwhile.

Top doc’s honesty inspiring

Surgeon General Jerome Adams’ revelation about his health frailties is a powerful example of the racial disparity among coronavirus victims reported Wednesday.

African Americans make up 28 percent of New York City deaths from COVID-19, although blacks are only 22 percent of the population. Hispanics are 34 percent of fatalities, while comprising 29 percent of residents. Underlying health problems exacerbated by poverty are believed to be the cause of the inequality.

Adams, 45, who grew up on a farm in Maryland, personalized the tragic data by divulging his own medical problems.

“I have high blood pressure . . . I have heart disease . . . I actually have asthma and I’m pre-diabetic, and so I represent that legacy of growing up poor and black.”

It is awe-inspiring that this gentle, reassuring presence on the coronavirus task force has overcome adversity to reach the heights of medical leadership in America’s hour of need. It is terrible that he suffers from this debilitating childhood legacy, but his willingness to share his personal history will increase understanding of the effects of racial inequality and go some way to remedying it.

By contrast, Rep. Alexandria Ocasio-Cortez, whose district is among the hardest hit by the virus, blamed “environmental racism” and demanded coronavirus “reparations.” Her words will have the opposite effect.

Queen’s wisdom bucks us all up

British Prime Minister Boris Johnson was admitted to a hospital in the second week of his coronavirus infection. Somehow, it makes us feel more vulnerable when world leaders are struck down. But the stoic wisdom of a 94-year-old great-grandmother stiffened our spines.

“We will be with our friends again. We will be with our families again. We will meet again,” Queen Elizabeth said on British television.