Internet search patterns reveal clinical course of COVID-19 disease progression and pandemic spread across 32 countries

Effective public health response to novel pandemics relies on accurate and timely surveillance of pandemic spread, as well as characterization of the clinical course of the disease in affected individuals. We sought to determine whether Internet search patterns can be useful for tracking COVID-19 spread, and whether these data could also be useful in understanding the clinical progression of the disease in 32 countries across six continents. Temporal correlation analyses were conducted to characterize the relationships between a range of COVID-19 symptom-specific search terms and reported COVID-19 cases and deaths for each country during the period of January 1 through April 20, 2020. Increases in COVID-19 symptom-related searches preceded increases in reported COVID-19 cases and deaths by an average of 18.53 days (95% confidence interval 15.98 to 21.08) and 22.16 days (20.33 to 23.99), respectively. Cross-country ensemble averaging was used to derive average temporal profiles for each search term, which were combined to create a search-data-based view of the clinical course of disease progression. Internet search patterns revealed a clear temporal pattern of disease progression for COVID-19: Initial symptoms of fever, dry cough, sore throat and chills were followed by shortness of breath an average of 5.22 days (95% confidence interval 3.30 to 7.14) after initial symptom onset, matching the clinical course reported in the medical literature. This is the first study to show that Internet search data can be useful for characterizing the detailed clinical course of a disease. These data are available in real-time and at population scale, providing important benefits as a complementary resource for tracking the spread of pandemics, especially during the early stages before widespread laboratory testing is available.