What mobility data tells us about COVID-19’s path in the U.S.
To explore more data on COVID-19, please go to covid19.topos.com.
Epidemiologists have analyzed genetic samples of COVID-19 to understand the virus’ pathway across the U.S. from the first case in Washington state in January to today where more than 1.8 million cases have been reported. The research has suggested that over 60 percent of the cases in the U.S. can be traced to New York City based on genetic mutations of 23,000 virus samples from across the country.
Using Social Distancing Metrics provided by Safegraph, we looked at the relationship between visits originating from the five boroughs / counties of New York City to other U.S. counties and COVID-19 cases and deaths to see if there was supporting evidence for the genetic analysis. We also looked at four other potential points of entry to the U.S.: San Francisco, Los Angeles, and Chicago (based on airports where passengers were screened as a precaution by the CDC in January) and King County, WA (site of the first infections in the U.S.) to see if there were correlations between visits originating from those locations to COVID-19 cases and deaths in other counties.
The data reveal a strong, statistically significant correlation between visits originating from Manhattan in January 2020 to the number of COVID-19 cases and deaths reported by counties as of late May (r = 0.717 for cases, r = 0.696 for deaths). The correlations remain similarly strong (and statistically significant) for the months of February and March.
There is also a moderately strong correlation between visits originating from Brooklyn and cases and deaths in the same months ranging from 0.609 to 0.665. What these relationships allude to is domestic travel originating from NYC, specifically Manhattan and Brooklyn, seeded COVID-19 cases in far corners of the country in the first quarter of 2020.
We also looked at visits originating from counties home to three international travel hubs in the U.S. (San Francisco, Los Angeles, and Chicago) as well as King County, Washington. The data reveal very weak correlations between visits and cases and deaths. This aligns with the finding that the outbreak in New York City was the likely originator for outbreaks in other parts of the country.
You can explore visits originating from counties across the U.S. from January to May 2020 in our interactive map here.
Please note that Safegraph’s mobility data captures ~10 percent of mobile devices in the U.S. so visit counts are derived from a sample of the U.S. population.
Data Sources:
- COVID-19 cases and deaths by county, The New York Times (source)
- Social Distancing Metrics, Safegraph (source)
To explore more data on COVID-19, please go to covid19.topos.com.
