Experts say COVID-19 first came to Orange County through the wealthier coastal communities, like Newport Beach, Laguna Beach and Corona del Mar.
But now cases are highly concentrated in low-income Latino communities in cities like Santa Ana and Anaheim.
Dr. Daniel Parker, an epidemiologist at the University of California Irvine specializes in mapping out infectious diseases.
"This started in affluent communities on the coastal area," Parker said. "These are people who may have had stronger ties to places in Europe that at the same time had epidemics going on."
At the same time, he noted, it is likely that less testing was available in cities like Anaheim and Santa Ana. So there may have been more cases that went undiagnosed at that time, leading to a greater spread.
Orange County sees second-highest number of coronavirus cases in California
He says it may be that those lower-income communities have a higher concentration of "essential workers" who have to interact with the public for their jobs, such as grocery store workers and delivery drivers.
The wealthier communities, on the other hand, may have more people who have the luxury of being able to work from home and stay away from possible contact with the virus.
Maps show the disease's progression over time, with about five ZIP codes in the county being considered the worst hot spots.
To help track the virus, UCI, the Orange County Health Care Agency and community-based organizations are training hundreds of people from the most-impacted communities to help trace the spread of the disease in their neighborhoods.
Richer areas of LA have more access to COVID-19 testing, data show