The coronavirus doesn't behave the same way in all patients, and that may be because there are different variations of the virus across the United States.
According to a study from researchers at Northwestern Medicine, which has not yet been peer-reviewed, three distinct variants have been identified in Chicago, and are associated with different patterns of spread.
One is most closely related to variants centered in New York, which showed evidence of rapid spread across the U.S.
Patients with this variant were found to have significantly higher viral loads than those infected by the second variant. which researchers say is localized primarily in the Chicago area, and appears to be directly related to the early outbreak in China.