While every case is different, the telltale symptoms of the novel coronavirus have been widely agreed upon - a fever, persistent cough or shortness of breath. In the most severe instances, those afflicted have reported confusion or difficulty breathing, and sometimes, anxiety is the most prevailing symptom of all.
But a team of British ear, nose and throat doctors on Friday raised the possibility of a new indicator of the coronavirus, one they say has been observed globally, even in patients who are otherwise asymptomatic: anosmia, a condition that causes the loss of sense of smell. In a statement, they warned that adults experiencing recent anosmia could be unknown carriers of COVID-19, the disease caused by the novel coronavirus.
"All of this evidence is accumulating very rapidly, but there's nothing yet robustly in print," Claire Hopkins, president of the British Rhinological Society, said in an interview. "Since then, I've had colleagues from around the world saying: 'That's exactly what we're seeing.' They've been trying [to raise awareness], but it hasn't been picked up."
Experts at the World Health Organization say they have not confirmed that loss of smell or taste is a symptom of the coronavirus, but they have not ruled it out.
Hopkins, who published the statement along with Nirmal Kumar, the president of ENT UK, a body that represents, ear, nose and throat specialists in Britain, said she was driven by recent discussions on rhinological discussion boards related to the coronavirus pandemic. There, she observed ENT UK's reporting a surge of reported anosmia across their patients, and even among themselves.
In their statement, Hopkins and Kumar cited reports from South Korea, China, Iran and Italy, where, they wrote, “significant numbers of patients with proven COVID-19 infection have developed anosmia/hyposmia,” the latter of which signals a reduced ability to detect smells. In Germany, they wrote, more than two-thirds of confirmed coronavirus cases included anosmia. And in South Korea, a country that has seen ample COVID-19 testing, “30 percent of patients testing positive have had anosmia as their major presenting symptom in otherwise mild cases.”
"This week, I saw nine patients that lost their sense of smell, which is unheard of in my practice," Hopkins said. "They were almost all under 40, and they were all told not to self-isolate."
Anosmia and hyposmia are historically linked to early symptoms of upper-respiratory infections - including previous strains of coronavirus - because the virus damages olfactory bulbs that are involved in the sense of smell. But Hopkins raised concern at the number of COVID-19 patients who were otherwise asymptomatic. She pointed to guidance in the United States and Britain that instructs people to self-isolate if they are experiencing obvious coronavirus symptoms.
Hopkins said she hopes that flagging another potential system will resonate with those who haven't taken social distancing and self-isolation seriously enough - the ones who do not realize they may carry the virus.
"The lack of awareness allows these people to carry on," she added. "This potentially gives us an opportunity to capture some of those people who are silent spreaders of disease. The patients I'm seeing haven't had a cough or fever at all."
Citing the ENT UK statement, the American Academy of Otolaryngology on Sunday wrote that in the absence of allergies, sinusitis or rhinitis, the loss of smell or taste should "warrant serious consideration for self-isolation and testing."
“Anosmia, in particular, has been seen in patients ultimately testing positive for the coronavirus with no other symptoms,” the academy wrote. “We propose that these symptoms be added to the list of screening tools for possible COVID-19 infection.”
Reports of anosmia appearing as a possible symptom of coronavirus have reverberated online in recent days. In response to a news article on the topic, Daniel Goldman - the former lead investigative counsel for the House Intelligence Committee Democrats who said last week he and his wife had tested positive for COVID-19 - wrote on Twitter that “this has been the case with both my wife and me.”
Rudy Gobert, the Utah Jazz center whose positive novel coronavirus test prompted the National Basketball Association to shut down entirely, said Sunday that he, too, had lost his sense of smell.
Thomas Hummel, an ear, nose and throat expert at the University of Dresden in Germany, said Monday he wasn’t surprised by the reported link between COVID-19 and anosmia. While he understands the need for urgent measures to slow the virus’s spread, he warned that many people are functionally anosmic - including about 5% of Germans - and reiterated that it will take more data to prove a true correlation.
He said the warning, without further research, could cause panic even among those who have long suffered from anosmia, further straining outpatient clinics. (For those experiencing short-term anosmia, Hummel and Hopkins agree that the sense of smell typically returns as the body recovers).
"On one end, it would be nice to have a good study. On the other hand, it's about not spreading the virus," he said. "Many people out there have anosmia. They don't have a good sense of smell. And if you alert all these people that if you have anosmia you need to stay home, there would be many false positives. That's the other side of the coin."
WHO experts expressed a similar sentiment, announcing Monday they have not yet confirmed the loss of smell or taste as a symptom of the coronavirus.
"We don't have the answer to that yet, although there's quite a bit of interest in this online," Maria Van Kerkhove, head of WHO's emerging diseases and zoonoses unit, said at a daily news briefing Monday.
Van Kerkhove said a number of countries were collecting data on the symptoms of early infections, and that WHO is working to learn if they have identified the loss of smell or taste as a symptom.
"We have a good handle on what the major ones are: Those are fevers. This is dry cough, and this is shortage of breath," said Van Kerkhove, adding that aches and pains and headaches were also found. Some patients, though "very few" overall, had reported gastrointestinal problems, runny noses or sneezing.
But still, Hopkins said the tendency to focus on the major symptoms could further perpetuate the spread of the virus.
“While there is a chance the apparent increase in incidence could merely reflect the attention CovID-19 has attracted in the media, and that such cases may be caused by typical rhinovirus and coronavirus strains, it could potentially be used as a screening tool to help identify otherwise asymptomatic patients, who could then be better instructed on self-isolation,” Hopkins and Kumar wrote.
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The Washington Post’s Adam Taylor and Cindy Boren contributed to this report.