Most of us are flunking handwashing. That’s an important public health message at any time, but especially during the height of the winter influenza season — one complicated by the emergence of COVID-19, the name given to the coronavirus that got its start in Wuhan, China, and has since spread across the world.

While researchers put the rush on developing treatments for this new pathogen, it’s good to remember how powerful low-tech, individual interventions like handwashing can be in combating disease. But doing it properly is key. That’s why it’s worth revisiting a Mayo Clinic doctor’s 2016 appearance on the Jimmy Kimmel Live! late-night talk show. The video is now on YouTube and Mayo’s web site.

Dr. Greg Poland, an infectious disease and vaccine specialist, flew to Los Angeles to do a handwashing tutorial for Kimmel, his sidekick Guillermo Rodriguez and the show’s viewers. The event took place in a men’s room, and Poland doesn’t waste any time in critiquing inadequate handwashing habits. “Almost nobody knows how to do it,’’ Poland said.

The subsequent footage bears this out. Poland puts gel on the pair’s hands to mimic bacteria, viruses and other unwelcome substances that too often lurk there. Kimmel and Rodriguez both do a quick wash with soap and water. Their casual rinse looks familiar to anyone who has used a public restroom.

When the lights are dimmed, a black light wielded by Poland shows hands that aren’t even close to clean. The leftover gel glows around the pairs’ fingernails, on their hands’ sides, and especially, their thumbs. “People always forget their thumbs,’’ Poland said.

Thorough handwashing, according to Poland, involves a good 20 to 30 seconds of vigorous scrubbing, starting from the fingertips and working up the hands from there. Kimmel likened it to rubbing the hands together in prayer and petitioning a heavenly pass from the cold virus. Drying hands completely is also important. Using a paper towel to avoid touching germy door handles on the way out is a good idea, too.

The video may be vintage, but its message remains important. Good handwashing could prevent two colds a year, Poland said. This six-minute refresher course is humorous but not entirely good clean fun. This was done for late-night TV and the language is aimed at an adult audience. To see the segment, or catch it again, go to tinyurl.com/rgt5h3d.