COVID-19 transmission high in Latino households of Baltimore, study finds

Latinos in Baltimore have high rates of household transmission of COVID-19, according to a recent Johns Hopkins University study published in Clinical Infectious Diseases.

The study found that in Latino homes in Baltimore, one in two people with COVID-19 passes it to others in the same household—a much higher risk than the average one in five found in similar studies around the globe.

Study co-author Diego Martinez, an assistant professor of emergency medicine at the School of Medicine and a member of the Whiting School of Engineering's Malone Center for Engineering in Healthcare, said that the findings provide new insight into why Latino communities have suffered disproportionately from COVID-19.

"Even now, we continue to see that socially marginalized groups are being hit hard by the pandemic," Martinez said. "Our findings suggest that Latinos face a high risk of catching COVID-19 in their homes. If we understand what is driving these disparities, we can help communities develop the appropriate interventions."

In their study, the researchers used data from free, community-based testing sites to investigate the likelihood of one household member infecting another, called the secondary attack rate, or SAR. Starting with 277 primary positive COVID-19 cases, the team identified an additional 638 "at-risk" individuals who lived at the same address. Using advanced modeling techniques, the SAR was calculated as the percentage of at-risk individuals who later tested positive for COVID-19.

Results from the study revealed that the SAR among Baltimore Latino households was 45.8%, significantly higher than rates found in other studies. For comparison, a recent study by the Centers for Disease Control and Prevention estimated that the SAR in the U.S. overall is 38%.

The Hopkins team also looked at how quickly the virus spreads in these households; they found the average time to the secondary diagnosis from the date of the primary case was fewer than two days.

According to Kathleen Page, study co-author and an associate professor of medicine at the School of Medicine, one common explanation for these findings is that Latinos are more likely to live in high-density or multigenerational homes, therefore facing higher transmission risk than non-Latino white households.

"Our study included mostly low-wage-earning Latino immigrants, many of whom are not eligible for safety-net benefits. In this community, it is very common to see several families or co-workers share living spaces, including crowded basements, where it is virtually impossible to isolate," said Page. "Unless we start to address the underlying factors that lead to crowded living conditions such as poverty and low wages, these communities will continue to be at high risk of exposure."

The team also notes that the dominant strain circulating when the study was conducted was the alpha variant. With the delta and omicron variants now identified, the researchers predict that the SAR in Latino households will only increase, especially for unvaccinated households.