To prevent catching the novel coronavirus, do as public health officials say, not as they do.

That means not touching your face. The advice is simple, but the task is herculean, even for those dispensing it.

Sara Cody, the public health director for Santa Clara County, Calif., slipped up at a news conference Friday, for example. “Start working on not touching your face,” she said.

Less than a minute later, she raised hand to mouth and licked her finger to turn a page in her notes. As of early Thursday, almost 4.5 million people had watched the clip shared on Twitter.

Coronavirus instructions.
Wait for it…https://t.co/WvnKBwKUtb

— Rex Chapman🏇🏼 (@RexChapman) March 4, 2020

That same day in Washington, Rep. Alexandria Ocasio-Cortez (D-N.Y.) scratched her nose and repeatedly brushed her hair away from her face while answering reporters’ questions at a news conference on covid-19 precautions.

.@RepAOC @AOC speaks to media on #coronavirus: "One of the key parts to preventing transmission is washing you hands and not touching your face…A mask will not protect you if you don't wash your hands and if you continue to touch your face." pic.twitter.com/WNmC3pLAUP

— CSPAN (@cspan) February 28, 2020

The trend continued Wednesday when Debbie Birx, coronavirus response coordinator for the White House, and Robert R. Redfield, director of the Centers for Disease Control and Prevention, who have both stressed the importance of the no-touching-your-face rule, touched their faces during a covid-19 task force briefing with President Trump.

“I haven’t touched my face in weeks — in weeks,” Trump jokingly said during the briefing. “I miss it.”

But as many people pointed out on Twitter, Trump has been caught on camera touching his face several times in recent days.

And who can blame him? Touching your face feels as natural as blinking.

“It’s very hard to change, because you don’t even know you’re doing it,” William Sawyer, a family doctor in Sharonville, Ohio, told The Washington Post on Wednesday.

As The Post’s Reis Thebault reported, face touching is a habit we’ve been reinforcing since we were born.

In 2015, researchers observed a class of medical students during a lecture in which they averaged 24 face touches an hour.

“The Daily Show With Trevor Noah” latched onto the trend Wednesday, compiling examples of five public officials, ranging from governors to World Health Organization representatives, touching their faces while giving press statements about preventing coronavirus.

Other offenders include Florida Gov. Ron DeSantis (R), New York Mayor Bill de Blasio (D) and Michael Ryan, executive director of the World Health Organization’s health emergencies program.

EXPERTS: Don’t touch your face.

ALSO EXPERTS: pic.twitter.com/OzcXvVR2Lz

— The Daily Show (@TheDailyShow) March 5, 2020

In the past several weeks, as anxieties over the novel coronavirus have increased, social media filled with memes, jokes and GIFs expressing people’s frustration with their inability to keep fingers off their faces.

“Realizing basically all I do is touch my face,” comedian and actor Seth Rogen tweeted Wednesday.

Doctors say keeping your hands off your face is the most effective measure you can take to avoid catching coronavirus and most other common viral infections. Frequently washing your hands with soap for 20 seconds, or using hand sanitizer, is another important precaution.

But if you end up touching your face despite your best efforts, know you’re not alone. Look no further than Vice President Pence, who is in charge of the covid-19 outbreak response, itching his nose seconds before shaking hands with the top public health experts working to prevent the spread of the virus.