In the first rounds of testing for COVID-19, county data showed coronavirus cases clustered in wealthier areas of Austin, but in a span of a week that trend seems to be reversing.

More than 40% of the county's 856 confirmed coronavirus cases are in the following ZIP codes as of yesterday:

Dell Medical School Dean Clay Johnston wrote in an April 3 email that residents in the wealthier neighborhoods may have traveled recently and include "big wigs (who shake a lot of hands and attend many events)." But he also suggested this trend was likely to change "because those now with the most contacts are in lower-paying positions."

While that seems to be bearing out, with cases migrating south and east, Dr. Elizabeth Matsui—a professor of population health and pediatrics and director of clinical and translational research at Dell Medical School—cautioned that the data is incomplete.

"At this point, the most that we could do is provide an educated guess or some ideas about what might explain [the caseload distribution]," she said during a phone interview last week.

Dr. Matsui added that caseload numbers may not be the most accurate metric.

"The positive test data by ZIP code is biased, meaning that it in part reflects who has access to testing, whereas the criteria for hospitalizing someone are more similar across groups of people," she said.

Since April 8, the city has provided hospitalization numbers, but the racial and ethnic breakdown of those hospitalized patients is not available. So far, the only group overrepresented among confirmed cases is non-Hispanic whites, who make up 49% of county population and 63% of those with positive test results.

"Different populations, in particular racial and ethnic minority populations, who, let's say on average have the same level of symptoms as a nonminority population, are very likely to be less likely to get tested," Dr. Matsui said.

Carmen Llanes Pulido—executive director of the nonprofit Go Austin/Vamos Austin, which advocates for health equity in East Austin—said this pandemic is exacerbating inequities.

"Yes, there's international travel," she said. "Yes, there's different kinds of exposure, but certainly the ability to get tested, I think, is directly connected to inequity."

Llanes Pulido added in a follow-up email that minority groups are also at higher risk of exposure.

"People of color are overrepresented in many of the jobs that are deemed essential right now: postal carriers, rideshare and delivery drivers, supermarket employees, construction workers, childcare providers for essential workers, etc. These communities also tend to have less financial security to miss work and are less likely to have paid sick leave and vacation time to allow them to stay from home," she wrote. "Many also do not qualify for unemployment."

Dr. Matsui said that until we have a larger data pool and demographic information on who is hospitalized due to coronavirus we will not have a clear idea of where disparities lie.

"We are hampered by the limited ability to tap into accurate, valid data," she said.