Transmission patterns of COVID‐19 have varied widely throughout the United States. Little is known about the reasons for such variability. This study examined the influence of four potential factors: urban vegetation, population density, air temperature, and baseline infection.
Baseline infection data was determined by the number of reported COVID cases from January 20 to March 13, 2020 in counties across the United States. It was during this time period that interventions were first instituted to slow COVID infections. The baseline infection data were then compared to COVID cases confirmed between March 14 and May 24. Only counties with a cumulative number of confirmed cases greater than 100 between March 14 and May 24 were used for analysis. A total of 989 counties met this criterion.
Of the four potential factors considered in this study, population density seemed to play the greatest role in directly regulating the spread of COVID‐19. Air temperature was negatively associated with cumulative COVID‐19 cases, but this association was not statistically significant. A comparison of baseline infection to cumulative cases indicated that “early implementation of control measures can effectively curb the spread of COVID‐19.” Counties with a relatively high cumulative number of confirmed cases also had a relatively low percentage of urban vegetation, “suggesting that a low proportion of urban vegetation coverage would facilitate the spread of COVID‐19.” The data supported this observation. Results showed that urban vegetation can play an important role in slowing the spread of COVID-19. As a mediator, urban vegetation regulates “the spread of COVID‐19 by weakening the associations between COVID‐19 transmission and population density as well as baseline infection.” The data indicated that “each 1% increase in the percentage of urban vegetation will lead to a 2.6% decrease in cumulative COVID‐19 cases.”
This research highlights “the importance of urban vegetation as a resilient infrastructure, especially in times of crisis.” Urban planners should thus consider increasing the proportion of vegetation coverage to better prepare cities for public health emergencies.
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