With respect to covid here’s where things stand as of now, based on my reckoning…
Prevalence. What percentage of the American population has been infected? We don’t know. The primary counting method relies on confirmed lab test results. However, for reasons outlined elsewhere, this method drastically underestimates the actual count. By how much? Five-fold? Ten? Twenty? Epidemiological studies involving small random samples, completed rapidly and at little cost, would provide an accurate estimate of true population prevalence. These studies have not been conducted.
Incidence. How rapidly is the virus spreading through the population? Again, we don’t know. Weekly random samples could track changes in the rate of infection. These studies are not being conducted.
Mortality. Death counts are more accurate than estimates of prevalence, though it’s acknowledged that the counts don’t include those who die from the disease without ever having been tested. However, prevalence is the denominator when calculating mortality rate, and there are no accurate prevalence numbers. Current models presume a mortality rate of maybe 0.5 percent, though the confidence intervals surrounding that estimate are wide. The actual rate could be as low as 0.15% or as high as 2%. For policy purposes we’re going to assume the lowest possible estimate.
Social Distancing. Current practice seems to be flattening the curve. Rates of confirmed infection and death, previously increasing geometrically, have stabilized over the past week. However, social distancing isn’t bringing the curve back down the other side. Since the daily number of newly confirmed cases and virus-related deaths peaked in early April, the numbers have not decreased. Another week of data collection, using the admittedly inaccurate present estimates of spread or, preferably, via systematic sampling, could indicate whether the current plateau will persist, or if new cases will begin to decline. If the rate declines, then new infections could drop to very small levels within a month or two. If the current plateau continues without dropping, then present social distancing practices would need to be kept in place for a year or more until herd immunity is achieved. There is no intention of waiting another week before changing public policy. Social distancing measures will be relaxed regardless of whether incidence has plateaued or is declining.
Containment. If new cases were to drop substantially over the next month, the initial pandemic wave will have infected maybe 5 to 10 percent of the populace (acknowledging again that these estimates are very rough and could be improved markedly with systematic sampling that’s not being conducted). That leaves the country vulnerable to new waves if current social distancing measures are relaxed. However, the lull in new cases would present an opportunity to initiate more targeted methods for stopping new outbreaks before they spread: widespread testing, quarantine of infected individuals, tracking of infected people’s social contacts. It would be possible to prevent new waves from getting started. If on the other hand new cases have merely plateaued and are not declining, then the task of getting ahead of the initial wave through targeted methods is rendered logistically impossible. The US does not presently have the technology, the organization, or the personnel to slow new waves with targeted methods, let alone to stop the current wave.
Herd Immunity. If the spread of this initial wave of infection plateaus under current social distancing measures, then the virus will continue to spread gradually through the population until maybe half of the population has been infected and achieved immunity. At the present rate that will take over a year to achieve. If current social isolation measures are relaxed, herd immunity will be achieved more rapidly, perhaps within 6 months, infecting maybe 70 percent of the population. The healthcare system, already stretched beyond its capacity, will be overwhelmed by patient loads doubling every few days until a new, higher apex is reached Deaths too will escalate rapidly. By the end of the year, total US deaths attributed to the virus will have mounted to between 330 thousand and 4.5 million, with maybe the most reliable estimate being around 1.1 million. For policy purposes we’re assuming that total deaths from herd immunity will be 300 thousand.
Differences by State. New York has been hit hardest. It has a large population, much of it concentrated in densely-populated urban zones that accelerate contagion. But California is also a large state with densely populated big cities, and its verified infections and deaths are much lower than New York’s. Some of the difference must be attributed to how rapidly stay-at-home orders were issued and followed once the first localized outbreaks took hold and began to spread. Less densely populated areas of the country might well benefit from intrinsically lower contagion rates. If a local outbreak does occur, however, a rural area has less reserve medical capacity to handle the overload of patients that would result. On the other hand, low-density areas have lower baseline case counts, so it’s conceivable that more targeted methods of containment — testing, quarantining, contact tracing — could be put in place before social isolation measures are relaxed, preventing local waves from building momentum. Most of the rural states are run by Republican governors and populated by Trump supporters, who resonate with the President’s obvious eagerness to make America open again without further ado. We’re going to open up the least densely populated half of the states ASAP without installing targeted containment methods.
The Old and Infirm. Based on limited demographic analyses, severity of covid illness increases with age and with comorbid health conditions. Maybe 60% of the hospitalizations and 85% of the deaths occur among those over 65 years old and those with heart, lung, or kidney disease. If those segments of the population were to self-quarantine as the wave washes across the population, then they can avoid getting caught in the rapid escalation of infection rates that will surely occur over the next 6 months. By staying out of circulation and not getting sick, the old and infirm can also limit the disproportionate burden they impose on the overextended medical system. They’ll also lower the death toll. Once herd immunity has been achieved, these vulnerable people can resume relatively normal social engagement in the world with limited risk of infection. We’re going to recommend that the old and infirm self-quarantine for their own safety while we open the country back up.
In today’s address to the nation Trump is going to declare that the worst is behind us and victory is ours. That’s clearly not true. If Trump were to justify publicly his policy pronouncements based on the truth, I’d be inclined to agree with them. However, it seems premature to give up on the possibility that current social distancing might actually bring the current wave to a halt, paving the way for rolling out proactive targeted methods that could limit new outbreaks and reduce future deaths to the kinds of small numbers experienced by places like South Korea and Australia. There’s no reason not to wait for another couple of weeks, conduct the necessary sampling studies, and see what’s actually happening before making uninformed policy decisions. That Trump won’t do it is damning.