Study finds 10% rate of COVID-19 in traced contacts in San Francisco
In a case study of COVID-19 contact tracing during San Francisco’s shelter-in-place period, of the 1,124 contacts traced, 1,017 (83.8%) were successfully notified, 457 (37.6%) were tested, and 120 (9.9%) were newly diagnosed.
In the study, published yesterday in JAMA Internal Medicine, the authors noted that contact tracers identified secondary cases within a median of 6 days from the person’s symptom onset.
The city’s sheltering in place lasted from Apr 13 to Jun 8, and officials recommended universal testing for all close contacts on May 5 whether or not they displayed COVID-19 symptoms. Of the 791 people the researchers interviewed after this new recommendation, 404 (51.1%) had a contact not previously diagnosed as having COVID-19, 356 (45.0%) had at least 1 contact notified, 206 (26%) had at least 1 contact that got tested, and 72 (9.1%) had at least 1 contact receive a positive test result for COVID-19.
Excluding long-term care facility outbreaks, the researchers reported 1,633 cases overall.
The researchers found that, similar to other studies, the secondary attack rate was higher for household contacts (11.3% vs 3.9%). Because of this, they hope that the period for testing and contact tracing can be decreased to prevent presymptomatic spread.
Also similar to other studies, minorities showed disproportionate rates of infection. Although San Francisco’s population is 15% Latino, they made up 70% of the study’s interviewed, infected people.
Nov 2 JAMA Intern Med study
Less distancing, higher COVID-19 burden in low-income neighborhoods
A study in Nature Human Behavior today finds a strong association between neighborhood income and physical distancing, with financial constraints and inability to work from home contributing to a higher COVID-19 burden in low-income neighborhoods.
Physical distancing—reducing close contacts between non-household members—is one of the primary strategies to mitigate the transmission of COVID-19 and was the impetus for state-level stay-at-home orders in the early months of the US pandemic. Data suggest that stay-at-home orders helped to reduce cases but reveal unequal declines and higher mortality rates among racial and ethnic minorities, who disproportionately live in low-income neighborhoods.
The study authors used cellphone mobility data from 19 million users in all 50 states and the District of Columbia from Jan 6 to May 3 to assess neighborhood-level physical distancing, finding increased physical distancing for all income groups, but lower increases for low-income communities. The highest income neighborhoods increased days at home 16.0 percentage points more than the lowest-income neighborhoods (P < 0.001, 95% confidence interval [CI], 16.0 to 16.1), inverting the pre-pandemic pattern of people in high income neighborhoods staying home less than those in low-income communities.
“The rapid inversion in the relationship between mobility and income during the COVID-19 pandemic illustrates how higher socioeconomic position affords greater opportunity to achieve good health,” the authors write.
Residents of low-income neighborhoods were more likely to work outside the home, showing only a 6.6-percentage-point reduction in days at work versus a 13.7-percentage-point reduction for the highest income areas. Non-work activities outside the home declined in all groups, with low- and high-income communities curtailing non-work activities at similar rates.
“Although lower-income individuals had the knowledge and motivation to avoid exposure to COVID-19, as their reductions in non-work activities suggest, they were less able to stop reporting to work outside the home,” the study authors conclude. “Our findings indicate that state policies did little to level the disparities in distancing between low- and high-income communities in Spring 2020.”
Nov 3 Nat Hum Behavstudy
Higher COVID-19 rates and mortality tied to substandard housing
Poor housing conditions are associated with higher US COVID-19 incidence and mortality rates, a PLOS One study yesterday showed, highlighting the need for health policies supporting individuals living in substandard housing.
Veterans Administration researchers conducted a cross-sectional nationwide analysis of 3,135 US counties used data from the US Centers for Disease Control and Prevention, the US Census Bureau, and John Hopkins Coronavirus Resource Center, identifying an average of 14.2% of US households living in substandard housing.
The authors defined poor housing as households that included one or more of the following characteristics: overcrowding (more than one person per room), high housing cost (greater than 50% of household monthly income), incomplete kitchen facilities (lacking a sink with running water, stove, range, or refrigerator), or incomplete plumbing facilities (lacking hot and cold piped water, a flush toilet, or a bathtub/shower).
The researchers calculated incidence rate ratios (IRR) and mortality rate ratios (MRR) for county-level COVID-19 cases and deaths on Apr 21, finding a 50% higher risk of COVID-19 incidence (IRR, 1.50, 95% CI, 1.38 to 1.62) and a 42% higher risk of COVID-19 mortality (MRR, 1.42, 95% CI, 1.25 to 1.61) for each 5% increase in percent of households with one or more substandard housing characteristics, with similar results for two earlier time points (Mar 31 and Apr 10).
The authors point to repeated exposure and potentially higher viral inoculum due to overcrowding and a lack of access to adequate plumbing and sanitation as the most likely factors responsible for the higher incidence and mortality. They advocate for the need for public health messaging to improve hygiene, surface cleaning, and ventilation in crowded housing.
“Our study adds to a robust body of evidence for other disease processes, which has shown that inadequate housing is a public health hazard especially in relation to infectious diseases and highlights the importance of finding short (e.g. better access to clean water and bathrooms) and long-term (e.g. overcrowding, cost) solutions to problems surrounding poor housing to help contain or mitigate the spread of COVID-19,” the authors wrote.
Nov 2 PLOS Onestudy