Loss of Smell and Taste Can Predict COVID-19 Instead of Flu

More than half of individuals with the coronavirus reported anosmia and dysgeusia, according to study results published in Microbes Infection.

The indications pertaining to COVID-19 and seasonal flu are not very different, but with a combination of symptoms, particularly loss of smell and taste for COVID-19 and a sore throat for the flu, predicting the possibility of being infected with either has become easier.

Although the symptoms of COVID-19 are similar to those of the seasonal flu, including chest pains, fatigue, fever, and a persistent cough, the addition of anosmia, the loss of anosmia and dysgeusia, or smell and taste is a big indicator of whether an individual has been affected with COVID-19.1

Investigators for a study in 2021 selected 1702 individuals who had an RT-PCR COVID test and symptoms, including loss of smell and taste. The number of individuals who tested positive was 579, and the number who tested negative was 1123.1

Of those who tested positive, 59.41% reported a loss of taste and smell, while 18.97% of those who tested negative reported the same symptoms.1

The investigators also concluded that the combination of abdominal pain, anosmia, diarrhea, fatigue, fever, loss of appetite, and persistent cough is most associated with a positive COVID-19 test and that individuals with a loss of smell and taste are 3 times more likely to have contracted COVID-19.1

However, the investigators mentioned that the study was limited and comprised a self-assessment of the participating individuals.1

Investigators from another study published in October 2020 compared the clinical features of seasonal flu and the COVID-19 pandemic.

They found that COVID-19 more frequently reported altered or loss of smell, diarrhea, a dry cough, frontal and retro-orbital headaches, or loss of or altered taste.2

Anosmia and dysgeusia after or during an influenza infection is possible, but it is uncommon. These symptoms are not clinical features of influenza like they are for COVID-19.2

The study results showed that 17% of the influenza group reported anosmia and 20% reported dysgeusia, while 53% and 49% of the COVID-19 group reported these symptoms, respectively.2

In addition, the mean duration of these symptoms for influenza (3 days) was significantly shorter than the duration from COVID-19 (7 days).2

In the study, 40% of the confirmed individuals with COVID-19 reported diarrhea, and investigators report that gastrointestinal symptoms could also be a tool to distinguish COVID-19 from the seasonal flu.2

However, there are a few differences when it comes to the flu that can help an individual determine if their symptoms are more flu-based or COVID-19-based.

In the results of the literature study, investigators found that a sore throat was more common for individuals with influenza than COVID-19. In addition, less than 5% of the COVID-19 group experienced bloodshot eyes, while 30% of the influenza group experienced this symptom.2

This study results also showed that roughly the first 5 days of both viruses have the 3 first symptoms appear in the same order. The first symptom was pain syndrome, followed by a fever and cough. The fourth symptom to appear, if it appeared at all, was diarrhea.

Individuals with COVID-19 also became critically ill later, usually around day 10 than individuals with the flu, around day 7.2

The investigators of this study analyzed data from 124 individuals, 70 with COVID-19 and 54 with influenza A/B.2

Thirty-three individuals with COVID-19 were hospitalized for a mean of 7 days. Of the 33, 23 individuals required oxygen therapy, and 11 were admitted to the intensive Care Unit for acute reparatory failure and needed artificial ventilation for 8 days.2

Investigators said their biggest limitation was the number of patients in the study.2

References

  1. Menni C, Valdes AM, Freidin MB, et al. Loss of smell and taste in combination with other symptoms is a strong predictor of COVID-19 infection. Nature Medicine. 2021; doi:10.1038/s41591-020-0916-2
  2. Zayet S, Kadiane-Oussou NJ, Lepiller Q, et al. Clinical features of COVID-19 and influenza: a comparative study on Nord Franche-Comte cluster. Microbes Infect. 2020;22(9):481-488. doi:10.1016/j.micinf.2020.05.016

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