Top news, reports and insights for today:
- U.S. COVID-19 cases now in flat but consistent growth; not to be confused with peak!
Today’s epidemic curve for daily U.S. cases (below) continues a pattern starting about April 1 of consistent daily growth in total cases. That means about the same number of cases are being added each day. In essence, we have gone from exponential growth in the first 3 weeks of March (cases doubling every 2-3 days), to additive growth until April 1 (doubling every 7-14 days), to flat growth (consistent adding of cases with daily fluctuations around a steady or flat rate of increase). It’s vitally important that people understand that flat growth does not indicate a peak in the epidemic. A peak in the epidemic cycle will occur when two conditions are met: 1) there is a period of sustained decline in daily new cases, and 2) the rate at which patients are recovering is greater than the rate at which new cases are added. Neither of these conditions has been met.
Why this matters? I see too many people making the leap from flat growth to a peak. A peak in the curves for daily cases is not the same as a peak for cumulative cases. If anything, the last five days have shown a return to gradual increases in daily cases. Several credible models I am monitoring suggest that in most states, we won’t see a peak in cases until anywhere from mid-May till early July.
- Antibody testing: A game-changer or a potential debacle?
Up till now, testing for COVID-19 has been done using a complex procedure that looks for telltale genetic fragments of the actual SARS-CoV-2 virus in a sample of fluid gathered on a Q-tip from someone’s nose or throat. That test tells us whether the virus is present in your body. It’s a complicated test that takes hours or days to run and it is far from perfectly accurate. A week ago, the FDA gave approval for a new kind of testing designed to do something different. The new approach looks for presence of antibodies in a sample of blood (that’s why it’s called serologic testing) to determine who has been exposed to the virus. This test can detect infection in people after symptoms have subsided when no active virus is present. More importantly, antibody testing can tell us who might be immune to the illness. This has tremendous potential to be a game-changer for surveillance (improving our ability to track the extent of the epidemic) and mitigation efforts (by determining who is protected). When widely available, this type of testing will be a boost to the health system by allowing us to determine which medical workers are safe to care for patients. The test may be done in the home and provides results in minutes. However, let’s not forget this is a fast-moving crisis and things rarely go exactly as planned. In approving these tests, the FDA has drastically lowered the bar on its evaluation and approval process. That means, lots of companies will rush products to market and some will not be accurate. Questions about accuracy will leave medical workers reluctant to abandon the need for PPE. Dr. Anthony Fauci recently said that antibody testing will be rolled out in a matter of days to weeks. They are already in use in China, Singapore and several other countries. The U.K. is planning to make them available for home use. It’s not yet known how well companies will be able to ramp up production, and distribution will be complicated as it has been with test kits and ventilators so far. Here are some important caveats to keep in mind as the nation gets ready to add this potentially powerful new tool to the fight against COVID-19:
- The test will require a blood sample. It’s not clear whether a finger-prick will be sufficient or whether a sample from a vein in the arm will be needed.
- Just because you detect antibodies, doesn’t mean you are immune.
- Antibody tests will be negative early in the infection. It takes time for the body to produce antibodies. The existing PCR test will still be better early in the disease.
- Some people don’t produce a strong antibody response to a virus, so the accuracy of the test will vary between people.
- Scientists don’t know how long immunity will last or whether re-infection is possible in those with antibodies.
- Developing an antibody test requires a lot of careful research. There hasn’t been time to fully vet the approach that is being relied upon.
- Quality control in the manufacturing of the test will not be optimal, so the accuracy will vary across manufacturer and batch.
- A tale of two states: My own look at Kentucky vs. Tennessee and what it tells us
An article by Dan Vergano in Buzzfeed news caught my eye on Wednesday. The article talks about how neighboring states Kentucky and Tennessee offer a natural experiment to compare 2 different responses to the COVID-19 outbreak. Attention to this comparison started with Kentucky resident Stephanie Jolly, whose graph showing the epidemic curves in the two states went viral last week. I decided to create and update my own version of the graph; hers plots cumulative cases, mine plots new cases by day. The graph shows daily lab-confirmed cases in the two states since March 10. As of yesterday, Kentucky reports 1,452 cases and 75 deaths, while Tennessee has tallied 4,634 cases and 94 deaths. Tennessee has a bigger population (6.8 vs 4.5 million) but even accounting for that, Kentucky has seen fewer cases and a flatter curve. The main story I take from this comparison is that early containment really mattered. Kentucky’s governor declared a state-wide emergency on March 6, while Tennessee waited till the 12th. Schools were closed in Kentucky on the 12th, Tennessee waited till the 20th. Restrictions on non-essential businesses and mass gatherings were a week earlier in Kentucky, and Tennessee didn’t finally issue a stay-at-home order until April 2. Basically, Kentucky moved a week to ten days faster to enact social distancing measures compared to Tennessee. It is speculation and not proof, but this early and decisive action by Kentucky governor Andy Beshear may have resulted in half the number of cases and a third fewer deaths. With the exception of April 8, new cases have been essentially flat in Kentucky since March 27. In Tennessee, dramatic rises in cases were seen in the last 2 weeks of March. As disease detectives, we will continue to monitor this and other state comparisons to gather clues about what is working and what is not.