Now playing
NYC mayor rejects mask mandate amid high Covid-19 alert
TOPSHOT - Employees spray disinfectant and wipe surfaces as part of preventative measures against the Covid-19 coronavirus at the Pyongyang Children's Department Store in Pyongyang on March 18, 2022. (Photo by KIM Won Jin / AFP) (Photo by KIM WON JIN/AFP via Getty Images)
Now playing
North Korea declares national emergency over reported Covid-19 cases
Now playing
Parents, children, superstars, and politicians killed by Covid-19
Johnson & Johnson's Janssen Covid-19 vaccine awaits administration at a vaccination clinic in Los Angeles, California on December 15, 2021. (Photo by Frederic J. BROWN / AFP) (Photo by FREDERIC J. BROWN/AFP via Getty Images)
Now playing
This is why you should still have confidence in the FDA for vaccines
Now playing
What we can learn from the WHO Covid mortality numbers
Now playing
Shanghai police barge down door in resident's apartment
Now playing
Dr. Ashish Jha predicts what's next with Covid-19
Now playing
See Dr. Gupta's reaction to judge ending mask mandate
Now playing
Dr. Sanjay Gupta reacts to 'abrupt' end of mask mandate for travelers
DULLES, VIRGINIA - MARCH 13: Passengers wearing masks arrive at Dulles International Airport March 13, 2020 in Dulles, Virginia. U.S. President Donald Trump announced restrictions on travel from Europe two days ago due to an outbreak of coronavirus (COVID-19). Today is the last day of unrestricted travel from Europe into the United States.  (Photo by Win McNamee/Getty Images)
Now playing
'Huge shift in travel policy': Travel mask mandate no longer in effect
WASHINGTON, DC - DECEMBER 21:  People pass a sign that reads "Face Mask Required" in a mall as COVID-19 cases surge in the city on December 21, 2021 in Washington, DC. District of Columbia Mayor Muriel Bowser reinstated the city's indoor mask mandate at 6am on Tuesday and announced a vaccination mandate for government employees after COVID-19 case numbers have surged to a new high.  (Photo by Alex Wong/Getty Images)
Now playing
This is how fraudsters peddled counterfeit Covid tests and masks
FILE - Customers wear face masks to protect against the spread of the coronavirus as they shop at the Reading Terminal Market in Philadelphia, Feb. 16, 2022.  COVID cases are starting to rise again in the United States, with numbers up in most states and up steeply in several. One expert says he expects more of a "bump" than the monstrous surge of the first omicron wave, but another says it's unclear how high the curve will rise and it may be more like a hill. (AP Photo/Matt Rourke, File)
Now playing
Business owners and residents sue Philly for reinstating mask mandate
Now playing
'Our priorities are skewed here': Doctor weighs in on Covid laxity
Now playing
China battles biggest surge in Covid cases since original Wuhan outbreak
china zero covid beijing winter olympics marketplace asia hnk _00012317.png
Now playing
How much longer can China's economy handle 'zero-Covid'?
CNN  — 

Loss of smell and taste is more severe in Covid-19 patients than in patients with common colds and that could be due to the effect the coronavirus has on the brain and nervous system, British researchers reported on Wednesday.

Loss of smell and taste is a symptom of Covid-19, but patients infected with coronaviruses that cause the common cold can also lose taste and smell because of congestion. The new research, described in a letter to the editor published in the journal Rhinology, suggests that loss of taste and smell in Covid-19 patients isn’t simply due to congestion in the nose.

“We know that Covid-19 behaves differently to other respiratory viruses, for example by causing the body’s immune system to over-react, known as a cytokine storm, and by affecting the nervous system,” Carl Philpott, of the University of East Anglia’s Norwich Medical School who was involved in the research, said in a news release on Wednesday.

“So we suspected that patterns of smell loss would differ between the two groups,” he said.

Philpott and his colleagues studied smell and taste function in 10 Covid-19 patients, 10 acute cold patients and 10 healthy people who served as a control group.

The researchers not only found that the smell and taste function of Covid-19 patients was significantly worse than in both the cold patients and the healthy individuals – but also the ability to detect sweet and bitter tastes was particularly impaired in Covid-19 patients.

“It is particularly interesting that Covid-19 seems to particularly affect sweet and bitter taste receptors, because these are known to play an important role in innate immunity,” Philpott said in the release.

Philpott called for additional research to explore the relationship between the virus and these taste receptors.

“It was this loss of true taste which seemed to be present in the Covid-19 patients compared to those with a cold,” he said in the release.

The researchers believe that loss of taste in Covid-19 patients isn’t just more severe, but is caused by a different mechanism in the olfactory system, which is responsible for the body’s sense of smell. The researchers say their findings indicate that Covid-19 patients are experiencing a direct loss of the ability to taste, rather than an indirect loss of taste because the sense of smell is impaired.

Covid-19 can produce increased inflammation throughout the body. The researchers suggest that this inflammation can damage taste receptors. They say it is also possible that Covid-19 can affect a part of the brain stem connected to the sense of taste.

Both the Covid-19 and cold patient groups in the study reported improvement in their sense of taste and smell over time, although only 30% of Covid-19 patients reported complete recovery.

The researchers say it is likely that a portion of the Covid-19 patients will experience persistent loss of taste after they clear the virus.

The research had some limitations, including the small study size. More research is needed to determine whether similar findings would emerge among a larger group of Covid-19 and cold patients.

Yet overall, Philpott and colleagues say smell and taste tests can discriminate between Covid-19 and cold patients, which means these tests could potentially be an additional screening tool for those with the novel coronavirus.

Get CNN Health's weekly newsletter

Sign up here to get The Results Are In with Dr. Sanjay Gupta every Tuesday from the CNN Health team.

The US Centers for Disease Control and Prevention includes a “new loss of taste or smell” on its list of Covid-19 symptoms to watch for.

“What’s called anosmia, which basically means loss of smell, seems to be a symptom that a number of patients developed,” CNN Chief Medical Correspondent Dr. Sanjay Gupta told CNN anchor Alisyn Camerota on “New Day” in July.

That symptom appears to be more prevalent in mild or moderate cases of Covid-19, and tends to appear at the beginning of the illness. It may even be one of the first signs that you are sick.

CNN’s Sandee LaMotte contributed to this report.