A report that examined Google search trends in 21 countries found that searches for “wash hands” predicted the spread of COVID-19. The report was published in Brain, Behavior, and Immunity.

On January 20, the person-to-person transmission of COVID-19 was officially declared by Chinese officials. In the following month, the coronavirus rapidly spread to parts of Europe and was soon a global concern. As public knowledge of the disease grew, people began to search for information on how to best protect themselves. This rampant desire for information is evident in Google search trends.

Previous research has found Google search trends to be indicators of public health, reflecting outcomes like infectious disease rates and mental health status in a given population. The current study wanted to examine how search trends might influence the spread of COVID-19 in different countries. Specifically, they investigated whether searches for “wash hands” and “face mask” would predict a slower spread of the virus.

Using Google Trends, researchers looked at the keywords “wash hands” and “face mask” among 21 countries between January 19, 2020, and February 18, 2020. Researchers counted the number of days during this time period where the Google Trend value was at least 25 above baseline, for each country. For a baseline measurement, researchers used the search interest for the same keywords from December 19 to January 18, before worldwide knowledge of the disease. They then compared this data to each country’s new cases of COVID-19 from February 19 to March 10.

Results were that the number of days between January 19 and February 18 when the trend value of “wash hands” increased by at least 25 from baseline, was negatively correlated with increased cases of COVID-19 from February 19 to March 10. In other words, an increase in searches for “wash hands” was associated with a slower spread of disease.

Across the 21 countries, queries related to the keyword “wash hands” included searches for hand washing steps and hand sanitizer brands. As the researchers discuss, “Google search for ‘wash hands’ indicated not only the promotion of hand hygiene awareness but might also reflect the extent that people proactively engaged in hand washing”. This improved hand hygiene might have served to limit the spread of the virus during the following 3 weeks.

However, while searches for “face mask” were at their highest ever in February 2020, an increase in searches for “face mask” had no impact on COVID-19 case numbers. The authors suggest that it is difficult to draw conclusions from this finding. “The increased search for ‘face mask’”, they explain, “might indicate the increased numbers of people wearing face masks, but also might result from the short supply of face masks in the corresponding country, which would indicate few people were wearing face masks”.

Still, the authors suggest that their findings indicate that even when wearing a mask, hand hygiene is important. Specifically, the practice of thoroughly washing hands with soap for a minimum of 20 seconds is crucial before applying the mask and again anytime the outside of the mask is touched.

The study, “Google searches for the keywords of “wash hands” predict the speed of national spread of COVID-19 outbreak among 21 countries”, was authored by Yu-Hsuan Lin, Chun-Hao Liu, and Yu-Chuan Chiu.