Loss of smell may suggest milder COVID-19, study finds

anosmia

New research suggests that loss of smell as a symptom of COVID-19 may indicate a mild case of the disease.

A new study has found that loss of smell, which is a reported symptom of COVID-19, may indicate that a person will experience a milder case of the disease.

The research, which features in the International Forum of Allergy & Rhinology, may be valuable in allowing clinicians to identify which COVID-19 patients require hospitalization and which may be able to self-treat the disease at home.

Overwhelmed hospitals

The sudden emergence of the SARS-CoV-2 virus and its rapid spread across the world have threatened to overwhelm the resources of hospitals. If a person develops a severe case of COVID-19, they will likely require admission to a hospital. If their condition continues to deteriorate, they may need to move to a critical care unit with access to a ventilator.

Although governments are attempting to provide the resources that hospitals need to cope with the significant increase in inpatients, many countries are nevertheless struggling to keep up with the number of people requiring hospital admission. This issue is particularly pertinent before a country has successfully "flattened the curve" by spreading new cases over a longer period.

Furthermore, following the widespread adoption of austerity measures in the wake of the financial crisis of 2008–2009, many hospitals and public healthcare systems are having to respond to the pandemic with already depleted resources. It is possible that this may have affected the quality of care that they are able to provide and increased mortality rates.

As a consequence, a key response to the SARS-CoV-2 pandemic has been to try to reduce the strain on hospital resources.

Loss of smell

One of the recognized symptoms of COVID-19 is the partial or total loss of the ability to smell.

In a correspondence piece in The Lancet Infectious Diseases, Dr. Michael Xydakis of the Department of Defense, United States Air Force Medical Services Corp, and his colleagues highlight that it is not yet clear why or how COVID-19 causes someone to lose their smell. However, their initial observations suggest that loss of smell "manifests either early in the disease process or in patients with mild or no constitutional symptoms."

The authors of the new research wanted to explore further how the loss of smell as a COVID-19 symptom relates to the severity of the disease.

If it is possible to confirm that people who experience loss of smell as an early symptom are less likely to develop a severe infection, hospitals may be able to ease the pressure on their resources by sending these individuals home to self-care.

Smell and COVID-19 severity

To conduct the study, the authors looked at data from 169 people who had tested positive for SARS-CoV-2. Of these people, 128 had data relating to their ability to smell or taste, so the team included these individuals in the final study group.

The authors found that the people who required hospitalization because of COVID-19 were far less likely to report that they had loss of smell or taste than those who did not need to stay in the hospital.

The senior author of the article, Dr. Adam S. DeConde, a physician in the department of surgery at the University of California San Diego Health, notes that "[p]atients who reported loss of smell were 10 times less likely to be admitted for COVID-19 compared to those without loss of smell."

"Moreover, anosmia [loss of smell] was not associated with any other measures typically related to the decision to admit, suggesting that it’s truly an independent factor and may serve as a marker for milder manifestations of COVID-19."

Dr. DeConde speculates that loss of smell may indicate that the severity of the virus depends on both where it infects a person and how much is able to enter their body.

He says: "The site and dosage of the initial viral burden, along with the effectiveness of the host immune response, are all potentially important variables in determining the spread of the virus within a person and, ultimately, the clinical course of the infection."

The authors note that their study had some limitations. For example, as it relied on people reporting their loss of smell, it may be that those who developed more severe cases of COVID-19 did not notice or think to mention that they were unable to smell.

Nonetheless, this research highlights an area that may be valuable to investigate in more detail. Furthermore, given the crisis of resources that healthcare systems are currently experiencing, the study may be valuable in helping clinical staff determine which patients require hospital admission and which can self-care at home, easing the pressure on hospitals.

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Timothy Huzar for MedicalNewsToday