- Researchers at Massachusetts General Hospital compared the volume of internet searches on certain gastrointestinal symptoms with the reported incidence of COVID-19 in 15 states between January 20 and April 20, 2020
- Searches on "ageusia," "loss of appetite" and "diarrhea" correlated most strongly with the rise in COVID-19 cases in five high-incidence states
- As the lag time between search volume and COVID-19 incidence increased, correlation increased, with the strongest relationship at three to four weeks
In 2009, Google employees showed that they could estimate weekly influenza activity in each region of the U.S. by monitoring internet search queries about flu-like symptoms.
Patients with COVID-19 often report gastrointestinal (GI) symptoms such as abdominal pain and diarrhea. Intrigued by the previous research, Ryan Flanagan, MD, MPH, former clinical fellow in the Department of Medicine at Massachusetts General Hospital, Kyle Staller, MD, MPH, director of the Gastrointestinal Motility Laboratory at the Division of Gastroenterology, and a colleague studied whether internet searches about GI symptoms could predict outbreaks of COVID-19. In a research letter published in Clinical Gastroenterology and Hepatology, they report that during the first weeks of the pandemic in the U.S., online searches about certain GI symptoms correlated with the incidence of COVID-19 in five states with a high burden.
The researchers made use of:
- Google Trends, an online tool that measures search term popularity, spatially and over time
- The Harvard Dataverse website, a source of daily figures on COVID-19 incidence by state
- Previous research on COVID-19 to identify common GI symptoms: abdominal pain, ageusia, anorexia, diarrhea, loss of appetite and vomiting
The researchers compared the search volume for each of the GI symptoms with the reported incidence of COVID-19 in 15 states between January 20 and April 20, 2020.
In most of the states studied, online searches for "ageusia," "loss of appetite" and "diarrhea" increased four weeks prior to the rise in COVID-19 cases.
During the study period, the five states with the highest burden of COVID-19 were New York, New Jersey, California, Massachusetts and Illinois. The maximum correlation between search interest and COVID-19 cases was:
- 0.998 for ageusia
- 0.871 for loss of appetite
- 0.748 for diarrhea
As the lag time between search volume and COVID-19 incidence increased, correlation increased, with the strongest relationship at three to four weeks. Searches on other GI symptoms did not consistently correlate with statewide increases in COVID-19 diagnoses.
A Novel Tool
GI symptoms appear to be a harbinger of COVID-19 infection. Google Trends may be a valuable tool for predicting geographic hotspots of COVID-19 and other epidemic diseases that have GI manifestations.
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