Daily COVID-19 Briefing: 4/19/20

Top news, reports and insights for today:

  1. Deaths decline, new cases holding steady in the U.S., Hot spots seen in the Midwest
    As the graph below shows, 1,743 new COVID-19 deaths were reported on Saturday, a rise of only 5%. This represents a significant decline over the steady pace of the four previous days (note the drop is greater than the error bars). New cases held steady Saturday, with 27,800 new confirmed cases reported. As usual, it is not clear if this is flattening the curve or the peak in testing capacity. We now have reason to believe there are 50-80 times more infections in the community than our testing can account for, and rates of testing appear flat (see yesterday’s briefing). The next graph looks at state and regional patterns in new cases. The states with the biggest three-day growth in new cases are in the Midwest, where four states stand out: North Dakota (+45%), Nebraska (+35%), Ohio (+30%), and South Dakota (+32%). Three of these four states (North and South Dakota and Nebraska) have still refused to issue stay-at-home orders (SAH). The latter is a fascinating case because although very sparse in population, South Dakota has seen the hottest hot spot in the country due to a massive outbreak at one Smithfield pork processing plant in Sioux Falls as reported by the BBC. After the first employee tested positive in late March, the plant, deemed an “essential” business, stayed open. On April 15, when it was finally closed due to pressure from the Governor’s office, a cluster of 644 confirmed cases had been identified, making it the number one hot spot in the US and accounting for 55% of the cases in the state. South Dakota provides a useful clue about how retraction of SAH orders will result in new hot spots in large manufacturing settings, even in very low density areas.
    What this all means? The drop in new deaths is welcome news and provides the first evidence of significant declines in daily deaths. But, it’s just one day. We can’t be sure we are at peak deaths until we see a sustained and consistent pattern of falling deaths. Flat growth in new cases most likely reflects the limits of our testing. Due to the unwillingness of the Federal government use resources to build testing capacity, we will continue to be in a tip-of-the-iceberg scenario. South Dakota offers a cautionary tale about the risks of re-starting the big economy.
  1. Antibody testing to the rescue? Not so fast.
    Yesterday, I was excited to report on the results of the Santa Clara County study using antibody tests of blood samples to estimate population seroprevalence. However, determining the spread of disease in a population for epidemic surveillance, and using antibody testing to determine who is currently infected or who is protected against further infection are completely different things. Currently, the FDA has approved 90 companies to distribute antibody testing in the U.S., and another 120 companies have submitted applications. In an excellent review today, the New York Times called it a “medical free-for-all“. Most of the approved tests come from China; their performance has not been scrutinized or properly vetted. As Michael Osterholm of University of Minnesota said: “People don’t understand how dangerous this test is……We sacrificed quality for speed, and in the end, when it’s people’s lives that are hanging in the balance, safety has to take precedence over speed.” We need only remember how bumpy the roll out of viral RNA testing has been to be cautious, but the rollout of antibody testing may be significantly more problematic. Here is what we know so far:
  • Antibody testing can and should not be used to determine who is actively infected or infectious, but it is being used in that way;
  • The rapid antibody tests are the easiest to administer and most in demand, but they have been found to be the most unreliable, yielding accurate responses in as few as 20% of tests;
  • The UK ordered over 3 million tests only to discover that those tests could not detect antibodies in those who weren’t gravely ill;
  • Test makers are routinely making false claims about their products with little oversight;
  • Manufacturing delays (in China and elsewhere) make it extremely unlikely that supply can keep up with demand, which is soaring as states clamor to return to business;
  • The most reliable tests rely on an technique called ELISA that is both expensive and time consuming;
  • Tests cost patients $60-115 with no assurances that they will be accurate;
  • Detecting the presence of antibodies does not confirm immunity;

The Bottom Line: Hope springs eternal that antibody testing will lead to “immunity certificates” that will tell us who is safe to return to normal life and get back to work. That hope is fueling a wild, wild west atmosphere, where unproven tests are flooding the market with inadequate vetting and no oversight. The rush to adopt antibody testing fails to account for the complexities involved. An antibody is not an antibody. It takes time to develop a test that can tell the difference between those specific antibodies that are able to neutralize the virus (aka provide actual immunity) versus those that cannot. The consequences of widespread reliance on flawed and inaccurate tests to determine who is infected and who is immune could have devastating consequences in an epidemic where asymptomatic transmission is occurring. Antibody testing will backfire if false positive results from rapid testing kits now in use in thousands of clinics, companies and doctor’s offices cause people to believe they are negative or immune when they are not. If you are offered a fast in-office antibody test, take my advice, and that of the WHO, and don’t take it.

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