Loss of smell linked to milder COVID-19 symptoms

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In a new study, researchers found that loss of smell often suggests the resulting COVID-19 disease is more likely to be mild to moderate.

The finding provides a potential early indicator that could help health care providers determine which patients may require hospitalization.

The research was conducted by a team at UC San Diego Health.

One of the immediate challenges for health care providers is to determine how to best treat persons infected by the novel coronavirus.

If they display no or mild symptoms, can they return home to self-quarantine or will they likely require hospitalization?

These are crucial questions for hospitals trying to efficiently and effectively allocate finite medical resources.

Previous research has shown the loss of smell and taste as indicators of SARS-CoV-2 infection.

In the study, the team suggests loss of smell may be predictive of a milder clinical course of COVID-19.

It appears that loss of smell may be a predictor that a SARS-CoV-2 infection will not be as severe, and less likely to require hospitalization.

If an infected person loses that sense, it seems more likely they will experience milder symptoms, barring other underlying risk factors.

The team examined 169 patients who tested positive for COVID-19 at UC San Diego Health.

They found patients who were hospitalized for COVID-19 treatment were much less likely to report anosmia or loss of smell (26.9% compared to 66.7% for COVID-19-infected persons treated as outpatients).

Similar percentages were found for loss of taste, known as dysgeusia.

The team says patients who reported the loss of smell were 10 times less likely to be admitted for COVID-19 compared to those without loss of smell.

Moreover, loss of smell was not linked to 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.

The researchers said that the findings possibly hint at some of the pathophysiological characteristics of the infection.

If the SARS-CoV-2 virus initially concentrates in the nose and upper airway, where it impacts olfactory function, that may result in an infection that is less severe and sudden in onset, decreasing the risk of overwhelming the host immune response, respiratory failure, and hospitalization.

This is only a hypothesis, but it’s also similar to the concept underlying live vaccinations. At a low dosage and at a distant site of inoculation, the host can generate an immune response without severe infection.

The team says the loss of smell might also indicate a robust immune response that has been localized to the nasal passages, limiting effects elsewhere in the body.

The lead author of the study is Carol Yan, MD, a rhinologist and head and neck surgeon at UC San Diego Health.

The study is published in the journal International Forum of Allergy & Rhinology.

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