COVID-19 patients can lose smell for weeks: Should 'smell tests' be part of screening?

The emphasis on fever screening can create a false sense of security, experts say.
/ Source: TODAY

The loss of smell or taste has emerged as a common symptom in patients with mild cases of COVID-19. Now a new study shows that while those senses return within a month for most people, some can struggle with the unsettling changes for longer.

About one-tenth of patients who complained of anosmia — the loss of smell — and dysgeusia — an altered sense of taste — reported the symptoms persisted or became even worse four weeks after they began, European researchers reported Thursday in JAMA Otolaryngology–Head & Neck Surgery. That doesn’t mean the patients were still contagious.

The results were based on answers from 113 adults who tested positive for COVID-19 and were seen at Treviso Regional Hospital in Italy in March. All reported the “sudden onset” of an altered sense of smell or taste two weeks before the initial swabs.

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When doctors followed up a month later, almost half — 49% — of the patients said the symptoms had completely resolved and almost 41% reported they were less severe. That left almost 11% with an impaired sense of smell or taste that was unchanged or worse.

“We didn’t really know what to expect because of course we don’t have experience with anosmia caused by this virus,” Dr. Daniele Borsetto, a study co-author and senior clinical fellow at Guy’s and St Thomas’ Hospitals in London, told TODAY.

“We know post-viral anosmia can last weeks. So overall, it’s not surprising.”

The virus behaves differently in different people, which may explain why some lose their smell for so much longer, he added.

There are high-profile examples of this phenomenon as well: Britain’s Prince Charles, who was diagnosed with COVID-19 in March, still had not fully regained his sense of smell and taste by mid-June, the BBC reported.

The focus on smell:

The loss of smell, in particular, has been seen in people who ultimately test positive for the new coronavirus while having no other symptoms, according to the American Academy of Otolaryngology — Head and Neck Surgery.

That’s led to questions about whether “smell tests” — in addition to temperature checks — could be an effective way to screen people for COVID-19 in airports, theme parks and other public places.

Taking smell loss into account would be helpful since the emphasis on fever screening can create a false sense of security, said Dr. Amesh Adalja, a senior scholar at the Johns Hopkins University Center for Health Security in Baltimore and a spokesman for the Infectious Diseases Society of America.

About half of people who are infected with the coronavirus may not actually have a fever or they may be taking medications that suppress it, he explained. Plus, thermal imaging is an imprecise method for scanning crowds.

“When you are screening people, I think it should be symptom-based, and loss of taste or smell should be something that should be incorporated along with a fever screening and other symptoms as well,” Adalja noted.

But there is currently no validated test for reliable screening of smell or taste in public areas, said Dr. Kris Jatana, associate professor of otolaryngology — head and neck surgery at Nationwide Children's Hospital and Wexner Medical Center at Ohio State University in Columbus.

Even if there were, a baseline test would be needed for accurate results since many people may not have a great sense of smell to begin with, regardless of their COVID-19 status, Borsetto noted.

Adalja also stressed it wouldn’t be practical to have people actually smell something to test their senses in airports and other public places. Instead, he believes they should just be asked about any altered sense of smell as part of the screening process.

“There are apps and ways to go through a checklist and ask, ‘Do you have any of these symptoms?’ If you do, you step out of the line and get an evaluation,” Adalja said.

“It’s important that we be inclusive of all the symptoms that we know are consistent with coronavirus.”

Borsetto and Jatana advised people to monitor themselves and pay attention to any changes in their usual sense of smell or taste. Rather than relying on a medical smell test, it’s extra important to be self-aware during the pandemic, Borsetto said.

“In view of a possible second wave, realize by yourself that you are experiencing a smell loss,” he noted.

“Individuals who feel they have had a change in smell or taste from their baseline, should self-quarantine and get tested for the coronavirus,” Jatana added.