In over a thousand patients with undiagnosed flu-like symptoms, experts found those with a loss of smell and taste had a 10-fold greater chance of testing positive for COVID-19.

"The most common first sign of a COVID-19 infection remains fever, but fatigue and loss of smell and taste follow as other very common initial symptoms," clarifies otolaryngologist and head and neck surgeon Carol Yan from the University of California San Diego.

The good news? If you're sniffing isn't up to snuff, it won't be forever, and it might actually bode well for your recovery.

Surveying 1,480 patients, researchers found just over 100 tested positive for COVID-19. Among this subset of patients, a profound loss of smell and taste was quite common, but these senses usually came back within two to four weeks of infection, matching the timing of disease recovery overall. 

"Among the COVID-19 patients with smell loss, more than 70 percent had reported improvement of smell at the time of survey and of those who hadn't reported improvement, many had only been diagnosed recently," says Yan.

Compared to a fever or fatigue, a profound loss of smell or taste can often go overlooked or be explained away, meaning that many people with this symptom could be 'hidden carriers' of the virus without even knowing it.

In response to their research, the university has added loss of smell and taste to its screening requirements for visitors and staff, and its medical professionals are now using this symptom as a possible marker for the virus.

Of course, this is just one study in a global race to better understand this deadly virus. Further research is not only necessary, it's inevitable. We still don't really know what the full gamut of COVID-19 symptoms is, or how varied they can be; both those answers will be crucial in how we move forward as a global community.

In the new study, for instance, a person with a sore throat was actually four to five times more likely to test negative for COVID-19, adding yet another way for physicians to distinguish between those who are infected and those who may not be. 

So far, South Korea, China and Italy have found about a third of patients who test positive for COVID-19 also report a loss of smell, and many have no other symptoms. The new research in the US seems to largely support that idea, albeit in a group with mostly mild cases.

Up to 71 percent of COVID-19-positive patients in this study reported an impairment in their smell and taste. Compared to other symptoms, the researchers say these signs showed the greatest association with COVID-19.

Unlike other studies, this research only looked at a subset of patients, most of whom were not hospitalised and none of whom required intubation. This is probably why the percentage is so much higher than what other countries have found.

In light of their results, the authors suggest that perhaps patients who are walking around with this disease show more symptoms associated with smell and taste, while those who experience a more "pulmonary-centric" infection might show different symptoms.

If this is true - and further research will need to investigate the idea - it could mean that a loss of smell might bode well for a person's overall recovery; they might not have as severe a response to the virus.

While there's still plenty more to learn, researchers in California think we know enough at this point to make a loss of smell and taste an official symptom.

"It is our hope that with these findings other institutions will follow suit and not only list smell and taste loss as a symptom of COVID-19, but use it as a screening measure for the virus across the world," says Yan.

ScienceAlert

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