U.S. COVID-19 total tops 760,000; test issues still exist

April 20, 2020

As COVID-19 cases in the United States passed 760,000, with over 40,000 deaths, researchers published early findings that suggest, as expected, the disease is more widespread than case numbers reflect. The global total stands at over 2,400,000 cases from 185 countries, with more than 165,000 deaths.

Testing issues continue to hobble state’s plans to ease off stay-at-home orders, and at a recent White House briefing, President Trump said the administration will be sending 5.5 million swabs to the states, though he signaled the governors have the capacity to provide them, CNN reported. In an interview with PBS, Vice President Pence said the administration is focusing on expanding unused capacity at labs.

In another testing-related development, contamination at a Centers for Disease Control and Prevention (CDC) lab delayed the distribution of COVID-19 tests to states, the Washington Post reported. Citing scientists with knowledge of the situation and federal regulators, the report said cross contamination probably stemmed from assembling chemical mixtures in a lab space that handled synthetic coronavirus material, a practice that didn't follow CDC procedures.

In other news, three new studies—two involving seroprevalence and one analyzing a home-based polymerase chain reaction (PCR) test—revealed early clues about how widespread the disease is in some U.S. communities.

A study of seroprevalence in Santa Clara County, CA, by a team based at Stanford University found that based on three scenarios for test performance, the population prevalence ranged from 2.49 percent to 4.16 percent, suggesting that 48,000 to 81,000 people in the county were infected by early April. They published their findings in the preprint server medRxiv.

The authors enrolled participants through Facebook ads, and the sample size included 2,718 adults and 612 children who were tested at one of three drive-through testing locations. At the time of the study, Santa Clara County had about 1,094 cases, the largest in northern California. The test kit, made by Premier Biotech, based in Minneapolis, was tested in Stanford labs before it was used to test study participants.

Researchers not involved in the study who weighed in on Twitter noted a "consent bias" in the study, meaning participants may have volunteered, because they had been sick with COVID-19. Natalie Dean, PhD, with the University of Florida Department of Biostatistics, on Twitter also raised concerns about unstable population weighting, wide uncertainty bounds after adjusting for clustering and test specificity.

In Chelsea, MA, a seroprevalence study of 200 city residents conducted this week by a team from Massachusetts General Hospital found that 64 (32 percent) had antibodies to the virus, the Boston Globe reported. The participants were generally healthy, though half said they had at least one symptom of the illness in the past four weeks. The city is one of the state's hot spots and earlier this week had recorded at 712 cases, at least 39 of them fatal.

Meanwhile, a home-based swab testing study launched on March 23 by the Seattle and King County health department and the Seattle Flu Study group found that of 4,092 samples, 44 (1.6 percent) were positive for COVID-19. In a blog post, researchers said the proportion of positive tests was lower than testing through the medical system but may still represent thousands of unrecognized community infections. Prevalence declined over the testing period, but the drop wasn't statistically significant.

The team urged caution in analyzing the findings because of the sample size and said it's too early to draw general conclusions from the data.

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