Negative Binomial Regression
	Number of COVID-19 Cases in County		Number of COVID-19 Deaths in County
	IRR	CI-95	IRR	CI-95
Distance to airport: Ref: >50 miles
25> Miles to airport	1.416**	[1.108]-[1.810]	1.657***	[1.273]-[2.156]
25-50 Miles to airport	1.210	[0.994]-[1.472]	1.210	[0.985]-[1.486]
Num. of airport	0.991	[0.957]-[1.025]	0.981	[0.943]-[1.021]
Volume of Airport Ref: No volume
Medium volume	1.779**	[1.246]-[2.542]	1.456	[0.985]-[2.152]
High volume	0.562	[0.261]-[1.208]	0.358*	[0.135]-[0.954]
Num. of train stations	0.985	[0.783]-[1.239]	1.050	[0.740]-[1.491]
Being in counties or nearby counties with major 13 Airports	0.477	[0.223]-[1.020]	0.462	[0.165]-[1.290]
Being an international airport	1.197	[0.852]-[1.683]	1.354	[0.902]-[2.032]
Commute Ref: Work from home
Drove alone	1.024***	[1.016]-[1.033]	1.029***	[1.019]-[1.040]
Carpooled	1.020	[0.979]-[1.063]	0.986	[0.943]-[1.032]
Public trans	1.155***	[1.063]-[1.255]	1.144**	[1.043]-[1.255]
Walked	0.917**	[0.869]-[0.969]	0.952	[0.892]-[1.016]
Other	1.011	[0.925]-[1.105]	1.051	[0.948]-[1.165]
Commute Traveling time	0.994	[0.968]-[1.022]	1.005	[0.970]-[1.043]
County Population
Total county population (/1000)	1.003***	[1.002]-[1.005]	1.004***	[1.002]-[1.006]
Population density (/100)	0.998	[0.996]-[1.000]	0.997*	[0.995]-[1.000]
N	2891		2891

*p < 0.05, **p < 0.01, ***p < 0.001.

Sources: JHU-COVID-19 Data (Updated May 5, 2020), Airport and Amtrak Station Data (2019), ACS Data (2018)

Notes:

1) All models have been controlled by race/ethnicity groups, population, population density, number of people at household, age categories and percent of poverty.

2) We have clustered errors by state to capture states policies and interventions.