Use of Google Trends to investigate loss-of-smell-related searches during the COVID-19 outbreak

Abstract

Background: Initial reports describing coronavirus 2019 (COVID-19) were dominated by the presence of cough, breathlessness, and fever; anecdotal reports suggested anosmia may also be a manifestation. We used Google Trends (GT) to investigate whether there was a surge in individuals searching for information related to smell loss during the COVID-19 epidemic in Italy, Spain, the United Kingdom, the United States, Germany, France, Iran, and The Netherlands.

Methods: GT was used to explore internet activity related to loss of smell in the 8 aforementioned countries. Spearman rank analysis was performed to correlate loss-of-smell-relative search volumes (RSVs), with the increases of daily confirmed cases of COVID-19 and deaths attributed to disease. As a control event, we also performed analysis of smell-related searches during the last UK influenza epidemic of 2009.

Results: In all 8 countries, we observed strong correlations between daily RSVs related to loss of smell, increases of daily COVID-19⁺ cases and deaths ranging from 0.633 to 0.952. All correlations were statistically significant (p < 0.05).

Conclusion: There is a strong correlation between the frequency of searches for smell-related information and the onset of COVID-19 infection in Italy, Spain, UK, USA, Germany, France, Iran, and The Netherlands. We hypothesize this may relate to a previously underrecognized symptom.

Keywords: COVID-19; Google Trends; coronavirus; loss of smell; symptom variation.

FIGURE 1

Cumulative trends of RSVs in Italy, Spain, and UK between February 3 and March 25, 2020. COVID‐19 = coronavirus 2019; RSV = relative search volume.

FIGURE 2

Daily increases of COVID‐19⁺ cases, deaths and RSVs trajectories for Italy, Spain, the UK, the USA, Germany, France, Iran, and The Netherlands. Italy: day 1 = February 11, 2020 (10 days before first death), day 44 = March 25, 2020; Spain: day 1 = February 23, 2020 (10 days before first death), day 31 = March 25, 2020; UK: day 1 = February 24, 2020 (10 days before first death), day 30 = March 25, 2020; Iran: day 1 = February 9, 2020 (10 days before first death), day 46 = 25th of March 2020; USA: day 1 = February 19, 2020 (10 days before first death), day 36 = March 25, 2020; Germany: day 1 = February 28, 2020 (10 days before first death), day 27 = March 25, 2020; France: day 1 = February 15, 2020 (10 days before first death), day 40 = March 25, 2020; The Netherlands: day 1 = February 25, 2020 (10 days before first death), day 30 = March 25, 2020. Daily increase = daily increases of COVID‐19⁺ cases. Daily deaths = daily increases of confirmed deaths secondary to COVID‐19⁺. COVID‐19 = coronavirus 2019; RSV = relative search volume.

FIGURE 3

Daily increase of influenza‐positive cases and RSV trajectories for UK. Day 1 = April 27, 2009, day 32 = July 2, 2009 (testing of influenza discontinued next day).

FIGURE 4

Comparison of RSV trend during current COVID‐19 outbreak and matching period in 2019. RSV = relative search volume. Italy: day 1 = February 11, day 44 = March 25; Spain: day 1 = February 23, day 31 = March 25; UK: day 1 = February 24, day 30 = March 25. RSV = relative search volume. COVID‐19 = coronavirus 2019.

FIGURE 5

Heatmap of Spain showing the new cases of COVID‐19⁺ cases (left) and RSV (right) on March 3, 2020. COVID‐19 = coronavirus 2019.