Are US Covid Infections on the Rise?

8 APRIL — The US case counts have plateaued over the past seven weeks, with daily fluctuations falling well within the expected range of random variation. However, as has been well and repeatedly documented, case counts greatly underestimate the number of new infections. For several months the ratio held steady at a rate of around 2.7 new infections for every new dx test-positive. Now, however, there’s evidence to suggest that the ratio is ticking upward — which would mean that the infection rate likewise is climbing. Here’s the rationale:

Covid deaths are the most accurate indicator of covid infections, with death lagging about 3 weeks after diagnosis.

The covid fatality rate varies based on age. The older a nation’s population, the higher its fatality rate. The median age in the US is 38, with an age-adjusted fatality rate of 0.65% of covid infections.

US covid vaccines have been administered disproportionately to the older, more vulnerable people. Immunizing most of the elderly effectively reduces the average age of the US population still vulnerable to infection.

Assume that the median age of unvaccinated Americans at risk of covid infection is 36 years — 2 years younger than the overall population. The age-adjustment algorithm reduces the estimated US covid fatality rate from 0.65% to 0.55%.

Using this revised fatality rate as the basis for a revised estimate of infection rate, then over the past month there have been 3.2 new infections for each new dx test-positive case — an increase of 20 percent over the previously stable ratio of infections to cases.

These calcs imply that the plateaued daily case rate disguises a 20% higher rate of new covid infections over the past month or so. That makes sense: younger people who get infected tend to experience less severe symptoms, and so are less likely to see a doctor and less likely to be tested for the virus. The current rise in infections will almost surely exhaust itself over the next two or three months as vaccinations are made readily available to all US adults and herd immunity is approached.


US Covid Endgame: It Could Have Been Better/Worse

The IHME projects that, by the end of May, the covid-19 pandemic in the United States will be nearly over. The estimated daily infection rate has declined from nearly 400K in mid-December 2020 to around 110K in mid-March; it’s projected to drop to 14K by the beginning of June. Similarly, daily deaths, having reached an early January peak of 3,200, now average around 1,100 and are projected to decline to just over 100 per day by the end of July.

So far the coronavirus has infected around 30 percent of the US population, while nearly a quarter of Americans have received at least one dose of the vaccine. By the end of May infections likely will have risen only slightly, but vaccinations will have more than doubled, putting the country at the threshold of herd immunity. Barring the emergence of a radically deviant mutation, covid-19’s presence in the American populace will dwindle to nearly nothing for lack of fresh bodies to infect. The toll: over 110 million infected, over 600 thousand dead.

For the past twelve months covid-19 has been the number one cause of US deaths overall. Particularly lethal for the elderly, the virus was also the leading cause of death for adults aged 35-44 and for each subsequent 10-year age grouping.

It could have been better. If the US had managed the pandemic as aggressively and persistently as Australia, only around 2 million Americans might have been infected, leading to a death toll of around 13 thousand.

It could have been worse. At the beginning of the outbreak the goal was to flatten the curve, reducing the rate of contagion in order to prevent the healthcare system from being overwhelmed. Despite at-times high plateaus punctuated by localized spikes, the curve was flattened. The virus follows its own mysterious trajectory, and its spread might have ebbed and flowed regardless of measures taken to prevent contagion. Still, the annual flu season came and went with rates of infection not even reaching the usual off-season baseline numbers — a dramatic viral suppression attributable in large part to social distancing measures implemented to restrain covid’s spread. Had the curve not been flattened, the highly contagious coronavirus would likely have infected three-quarters of the population within the first few months. The fatality rate for those infected would likely have doubled due lack of resources, of personnel, and of accumulated expertise in treating the condition. Three million Americans might well have died of covid-19 by the end of summer 2020.

Early on, it was expected that the development of a safe and effective vaccine would take at least 18 months. That R&D interval was cut in half, with the first vaccinations being administered 9 months after the start of the pandemic. Had the original timeline held steady, the US would likely have experienced twice as many infections — 200 million — and twice as many deaths — 1.2 million — before infection and immunization together brought about herd immunity and the end of the pandemic..