Expert: Patients With COVID-19 May Have Loss of Taste, Smell for Years After Infection, But Remain Unaware


Kai Zhao, PhD, director of the Nasal Physiology and Therapeutic Center in the Department of Otolaryngology at Ohio State University College of Medicine, discusses how patients who have experienced a loss of taste and smell following COVID-19 infection may be impacted by this symptom for years without realizing it.

Pharmacy Times interviewed Kai Zhao, PhD, director of the Nasal Physiology and Therapeutic Center in the Department of Otolaryngology at Ohio State University College of Medicine, on the dangers of the loss of taste and smell among patients who have been infected with COVID-19.

Alana Hippensteele: Hi I’m Alana Hippensteele with Pharmacy Times. Joining me is Kai Zhao, PhD, director of the Nasal Physiology and Therapeutic Center in the Department of Otolaryngology at Ohio State University College of Medicine and senior author of a study recently published in Med that showed that a loss of smell and taste is a common COVID-19 symptom that may persist for longer than patients even realize.

So Dr. Zhao, based on your study findings, how long may the loss of taste and smell persist for patients who have had COVID-19?

Kai Zhao: Yeah, based on the study, I think this is a very wide spectrum of duration of disease. So some of our patients who have COVID, even during the first wave, which is March 2020—they still have smell loss. So we don't know exactly for each patient how long they can have it, but we think there could be a range of symptoms with this duration—some could recover very quickly, [such as] in a few days or even 2 weeks, [but] some could persist over months, even years. The exact frequency or prevalence for these patients is still unknown, I think.

Alana Hippensteele: What did your findings show regarding how many patients were aware or unaware of the persistence of their loss of taste and smell after COVID-19 infection?

Kai Zhao: I think we can say that it's higher than the background or the normal general population. So we have about 50% of patients who have COVID-19 previously who don't report any ongoing smell or taste loss, but objectively, we find they have smell loss at the time of testing. Some of them, like I said, had the disease even years prior, and by that time they are clear of the virus, but still, they have some objective losses.

I think this could raise to a public health awareness [issue], because I think, for the medical field, as well as public health, smell and taste are our least [assessed sense in the] odor-sensory system. For example, every newborn baby will have a hearing test to see if they have any hearing deficit. I get an eye exam every year, but nobody gets a taste or smell exam. So we don't know objectively how these patients are doing, even though maybe some subtle losses were not even realized.

Taking hearing loss, for example, some of the elderly who may have hearing loss are unaware. So even visual losses, or some eyesight problems, you probably don't know where. So I think, we should raise awareness, maybe we need more objective surveillance of the disease progress and impact, especially on the smell and taste functions.

Alana Hippensteele: What are the implications of this lack of awareness regarding the persistence of this symptom for patients?

Kai Zhao: Well, I think we could be overlooking some of the impacts of smell and taste loss on the population. So we now have a large population who have now had COVID-19, and there could be a large number of patients who have smell loss that we overlook. This could affect their nutrition intake, or food intake, and it could have other health consequences that we're not aware of.

For example, the one major concern I have for people with smell and taste loss is that they may not be able to detect a gas leak—and that could be a danger—or detect fire or detect dangerous chemicals. There are some workers who test solvents, and we have patients who have actually been knocked unconscious working in a confined environment with solvents or with chemicals they weren’t aware of. So people with good smell function can detect that and leave or ventilate, but some patients with smell loss cannot detect that environmental danger, and that could be a real risk for them.

Alana Hippensteele: As a follow up, if a patient would like to assess smell and taste loss, how would they go about that?

Kai Zhao: I think there are commercially available testing tools out there. The one we use is the [National Institutes of Health (NIH)] toolbox. So the problem is many health clinics don't routinely test for smell and taste and don't have the right objective tools. So hopefully, by raising awareness, more clinics will purchase these objective tools, including the NIH toolbox, or there's the University of Pennsylvania smell identification test, which is also commercially available. Then they can have more testing on patients to let people know the status of their sensory function.

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