As social distancing policies relax and social mobility increases, the number of confirmed COVID-19 cases is rising fast. Is there cause for alarm?
Rising cases certainly shows that COVID-19 is not contained. For those still hoping for eradication of the virus, the spike in cases is bad news. But the likelihood that COVID-19 can be eradicated is becoming increasingly implausible. There have been over 10 million confirmed cases worldwide and over 2.5 million in the U.S. Since confirmed cases may represent about 10% of actual infections, this would indicate that there have been about 100 million infections worldwide and 25 million in the U.S.
During widespread enforced social distancing policies in the U.S., daily confirmed cases in reached just over 30 thousand in mid-April and then slowly declined to just over 20 thousand by early June. In terms of reducing COVID-19 cases, social distancing has had limited effect. Yet after relaxation of these measures, cases have resumed their climb and exceeded 45,000 in only three weeks. Thus, while social distancing policies cannot extinguish the COVID-19 outbreak, they may help prevent outbreak expansion. Perhaps more stringent policies can smother the outbreak, but this appears both questionable and politically intractable. In short, COVID-19 has too firmly established itself in the population.
If COVID-19 cannot be eradicated, what should be done about rising case numbers? Most importantly, the focus should shift to COVID-19 deaths and hospitalization numbers and away from number of cases. Here the track record of enforced social distancing measures is more positive. During enforced social distancing, the number of US COVID-19 deaths reached a maximum of about 2,300 per day in mid-April and subsequently declined to roughly 600 per day by mid-June.
And there is more good news. The number of COVID-19 deaths is not rising, even as cases have increased to new highs. This is apparent in numbers from states that have seen the largest rise in cases. In Georgia, the first state to end enforced social distancing, cases reached a nadir of 500 per day in mid-May, only to climb to 1,700 per day by end of June. During the same time period, deaths declined from 34 per day to under 10 per day. In Texas, another COVID-19 ‘hotspot,’ newly reported cases reached almost 7,000 by end of June after holding at under 2,000 cases per day for the first half of the month. Though hospitalizations climbed during this period, deaths did not increase. In Arizona, cases went from 1,172 on June 1 to 4,136 on June 26. While there was an increase in deaths in the first half of June, they declined again in the second half of the month. And hospitalizations declined during the month of June. The same trend is seen in California, where cases doubled in June even as deaths remained unchanged. And in Utah? As with other ‘hotspots,’ cases have more than tripled since the start of June, yet the number of deaths has held constant.
How have deaths become divorced from cases? One reason is better care for the sick after a difficult and costly learning process early in the outbreak. Another is emerging therapeutic interventions. But the biggest factor is cases spreading among the resilient population of otherwise healthy individuals, even as the vulnerable — those with pre-existing conditions — remain cautious and voluntarily maintain social distancing. This effect is captured as the average age of new cases plummets.
Selective protection of the vulnerable while the outbreak accelerates through the healthy population is a highly effective and sustainable strategy for ending the COVID-19 outbreak. And it bears minimal adverse health costs, saving the most lives overall. COVID-19 is 100-200 times less deadly to the otherwise healthy than to those with pre-existing conditions. The resilient population has little reason to fear COVID-19 and when the outbreak resolves in this population, the vulnerable can safely emerge with minimal risk.
This strategy assumes that herd immunity can be reached. Arguments against the ability to generate herd immunity for COVID-19 are still being made, but this is even as evidence suggests herd immunity is being realized. While much has been made of diminishing antibody levels as time passes after infection, T cells programmed to fight COVID-19 are present in cases when neutralizing antibodies are not detected. Besides, individuals do not produce neutralizing antibodies forever after an infection. Instead, they rely on memory cells to re-start antibody production only when they are later challenged with a new infection. Thus, low or diminishing antibody levels are no indication of a lack of immunity. One additional note of promise is that cross-immunity, the initially discounted theory that prior infection with different coronaviruses confers some level of immunity to COVID-19, is real and likely contributes to resistance.
Populations appear to be instinctively and naturally implementing a strategy of social distancing for the vulnerable even as the healthy emerge to become exposed and build herd immunity for the entire population. A rise in cases is expected in this strategy and is nothing to fear. It represents the beginning of the natural end for the COVID-19 outbreak. Mitigating a rise in cases, at least in the absence of significant spikes in deaths and hospitalizations, only unnecessarily prolongs the outbreak.
Marc Hansen earned a Ph.D. for Stanford University School of Medicine in cancer biology and is a professor of physiology and developmental biology at Brigham Young University.