A Lost Sense of Smell: All About the Strangest New Coronavirus Symptom

Loss of smell appears to be yet another symptom to watch for in people who otherwise are not extremely ill

Photo: Werayuth Tessrimuang/EyeEm/Getty Images

SSome people diagnosed with Covid-19 have lost their sense of smell and even the ability to taste food according to a statement this week from ENT UK, a British group representing ear, nose, and throat surgeons. The possibility has not been formally studied, but anecdotal evidence from doctors in multiple countries suggests health care providers should look for the symptom as a possible indicator of the coronavirus infection.

Total loss of smell, called anosmia, can be caused by many viruses, including various strains of both coronaviruses and rhinoviruses, both of which can cause the common cold. Partial loss of smell is called hyposmia. Either can be accompanied by a loss of taste, called dysgeusia.

“There is already good evidence from South Korea, China, and Italy that significant numbers of patients with proven Covid-19 infection have developed anosmia/hyposmia,” wrote Dr. Claire Hopkins, an ENT surgeon and professor at King’s College London, and Dr. B. Nirmal Kumar, president of ENT UK. “In Germany, it is reported that more than two in three confirmed cases have anosmia. In South Korea, where testing has been more widespread, 30% of patients testing positive have had anosmia as their major presenting symptom in otherwise mild cases.”

Some of the people in Germany who had anosmia were not congested, Dr. Clemens Wendtner, a professor of medicine at the Academic Teaching Hospital of Ludwig-Maximilians University of Munich, told the New York Times.

Anosmia can be triggered by other diseases, too — anything that blocks, disrupts, or kills the olfactory nerve cells high up in the nasal cavity. It’s usually not serious by itself and typically subsides in weeks or months. However, the sense of smell gradually declines with age, too, like eyesight and other bodily functions.

Anosmia can also be caused by high blood pressure, poor nutrition, seasonal allergies, Alzheimer’s and other diseases, and some medications according to Johns Hopkins Medicine.

For these reasons, it’s not yet clear if anosmia is a symptom of Covid-19, the respiratory disease caused by the coronavirus called SARS-CoV-2, or if people found to have Covid-19 and anosmia had lost their sense of smell for some other reason, says Dr. Mahalia Desruisseaux, an associate professor of internal medicine at Yale University School of Medicine and member of the Infectious Diseases Society of America.

But given what’s known about other respiratory viruses, including coronaviruses, it makes sense that Covid-19 could be causing anosmia, she tells Elemental.

“I have personally seen four patients this week, all under 40, and otherwise asymptomatic except for the recent onset of anosmia — I usually see roughly no more than one a month.”

A growing, confusing list of possible symptoms

Already, Covid-19 symptoms have proven frustrating for physicians and people who worry they might have the disease.

The three hallmark symptoms of coronavirus were long said to be fever, cough, and shortness of breath, distinguishing Covid-19 from a cold or flu. While these symptoms do appear in many if not most of the severe cases, an alarming number of people carry the disease with mild cold- or flu-like symptoms, or even no symptoms, spreading the virus unknowingly. Only formal testing can reveal for sure if someone is infected with Covid-19, and in the United States and elsewhere, limited testing capability has left many possible cases undiagnosed.

Loss of smell appears to be yet another one of many symptoms to watch for in people who otherwise are not extremely ill or perhaps don’t seem sick at all.

“There have been a rapidly growing number of reports of a significant increase in the number of patients presenting with anosmia in the absence of other symptoms,” Hopkins and Kumar write, citing medical discussion boards from all regions where Covid-19 is prevalent. “Iran has reported a sudden increase in cases of isolated anosmia, and many colleagues from the U.S., France, and Northern Italy have the same experience.”

“I have personally seen four patients this week, all under 40, and otherwise asymptomatic except for the recent onset of anosmia — I usually see roughly no more than one a month,” Hopkins says. “I think these patients may be some of the hitherto hidden carriers that have facilitated the rapid spread of Covid-19. Unfortunately, these patients do not meet current criteria for testing or self-solation.”

A doctor in Italy says people diagnosed with the coronavirus commonly tell of a spouse who had lost his or her sense of smell, suggesting the spouse carried the disease and passed it along but had no other symptoms, according to the New York Times story.

“With all these anecdotal references … we do need to study this more to see whether or not this is truly related to Covid-19,” Desruisseaux says. “Having said that, we shouldn’t negate that as a possible symptom.”

What doctors (and you) should do

The American Academy of Otolaryngology, citing the ENT UK statement, offered a definitive view of what physicians should be looking for. “Anecdotal evidence is rapidly accumulating from sites around the world that anosmia and dysgeusia are significant symptoms associated with the Covid-19 pandemic,” the group said in a statement. “Anosmia, in particular, has been seen in patients ultimately testing positive for the coronavirus with no other symptoms. We propose that these symptoms be added to the list of screening tools for possible Covid-19 infection.”

Dr. Peter Gulick, an oncologist and infectious-disease specialist at Michigan State University’s College of Osteopathic Medicine, interpreted the new information cautiously, stressing the need for more Covid-19 testing to reveal whether anosmia and dysgeusia are indeed indicative of the disease or occurring incidentally.

Health officials in the U.S. and other countries ask anyone who thinks they might have Covid-19 to self-isolate. Gulick suggests people who have lost their sense of smell or taste but have no other signs of illness should also “monitor for other symptoms such as fever, cough, shortness of breath.”

Just after this story published, and 24 hours after our interview, Desruisseaux reached out with an update: “We have been seeing more and more [anosmia] in our institution in younger individuals, in the absence of other symptoms… if someone is having anosmia, even in the absence of other symptoms, they should isolate themselves until they get tested for SARS-CoV2 so that they don’t transmit the disease.”

The coronavirus outbreak is rapidly evolving. To stay informed, check the U.S. Centers for Disease Control and Prevention as well as your local health department for updates. If you’re feeling emotionally overwhelmed, reach out to the Crisis Text Line.

Explainer of things, independent health and science journalist, author, former editor-in-chief of LiveScience and Space dot com.

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