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

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