There may be another addition to the growing list of strange possible symptoms of the new coronavirus: “Covid tongue.”
A British researcher who is helping to track Covid-19 warning signs is reporting more cases of infected people complaining of tongue discoloration, enlargement and other mouth problems.
“Seeing increasing numbers of Covid tongues and strange mouth ulcers. If you have a strange symptom or even just headache and fatigue stay at home!” Tim Spector, a professor of genetic epidemiology at King’s College London, tweeted this month.
He believes more than a third of COVID-19 patients, 35 percent, have non-classic symptoms of the disease in the first three days, so it’s important to draw attention to skin rashes, Covid toes and other warning signs that “go ignored,” he wrote.
Spector estimated fewer than 1 in 500 patients have "COVID tongue." The main symptoms he hears about are a "furry coating" of the tongue that can be white or yellow and can't be brushed away, and a scalloped tongue. The condition can be painful.
"It's a good reminder that there are so many different manifestations of this virus rather than just the classical ones," Spector, who is the lead investigator of the ZOE COVID Symptom Study that allows people to report symptoms via an app, told NBC News.
"The whole question of why we have this huge range of symptoms of the virus is still unknown."
Until there's more data, it's too early to add "COVID tongue" to any official symptom lists, but dentists, oral surgeons and other doctors looking inside people's mouths should be aware it might be one of the early signs of infection, he noted.
Other researchers have also reported tongue and mouth symptoms linked with the new coronavirus.
When doctors studied 666 patients with Covid‐19 in Spain, more than a tenth of them — 78 — exhibited “oral cavity findings,” according to a study published in the British Journal of Dermatology.
Of that group, 11 percent had inflammation of the small bumps on the tongue's surface; 6 percent had a swollen and inflamed tongue with indentations on the side; 6 percent had mouth ulcers; 4 percent had "patchy" areas on the tongue; and 4 percent had tissue swelling in the mouth.
The oral cavity “deserves specific examination under appropriate circumstances to avoid contagion risk,” the authors wrote.
Tongue or mouth issues — other than a sore throat — don’t appear on the list of Covid-19 symptoms compiled by the Centers for Disease Control and Prevention, though the agency acknowledged it's still learning more about the new coronavirus so the page doesn’t include all possible warning signs.
After all, the loss of smell and taste seemed to be a strange symptom at first, but is now considered one of the common manifestations and is part of the list.
Other yet-to-be confirmed sensations include “fizzing,” or a tingling feeling reported by some Covid-19 patients. Will “Covid tongue” be placed in a similar category?
“This is kind of in tune with all of the things about Covid," said Dr. William Schaffner, professor of infectious diseases at Vanderbilt University School of Medicine in Nashville, Tennessee. "When it burst upon the scene, as I like to say figuratively, we opened up our medical textbooks to Covid and there were only blank pages.”
Schaffner hasn’t seen cases of “Covid tongue,” but he has heard it discussed. It may not be that the mouth is vulnerable to the new coronavirus, but that Covid-19 may set up an immune circumstance such that other viruses such as herpes labialis — the herpes virus above the waist, or herpes simplex virus type 1, which causes an infection of the lips, mouth, or gums — may perhaps activate, Schaffner said.
Researchers still need to determine whether any mouth and tongue issues are indeed related to Covid-19, he added.
“People react differently to different illnesses,” said Dr. Waleed Javaid, director of infection prevention and control at Mount Sinai Downtown in New York.
But he wouldn't consider “Covid tongue” as a diagnostic tool for the disease at this time just because it seems to occur in a very small proportion of people, he noted.
The American Dental Association said it has been tracking developments of tongue and mouth issues experienced by COVID-19 patients since early on in the pandemic. The study published in the British Journal of Dermatology is in line with what ADA researchers have heard from colleagues and partners, it noted.
"Oral health is an important and vital part of overall health, and the ADA is continuing to examine the connection between the two as it relates to COVID-19," the association said in a statement.
The American Academy of Otolaryngology-Head and Neck Surgery could not immediately comment about whether cases of mouth and tongue issues have been reported by COVID-19 patients.