Health & Wellbeing

Modeling estimates over 100 million Americans had COVID-19 in 2020

Modeling estimates over 100 mi...
Matching estimates from the CDC, a new model indicates less than a quarter of coronavirus infections in the United States are officially reported
Matching estimates from the CDC, a new model indicates less than a quarter of coronavirus infections in the United States are officially reported
View 1 Image
Matching estimates from the CDC, a new model indicates less than a quarter of coronavirus infections in the United States are officially reported
1/1
Matching estimates from the CDC, a new model indicates less than a quarter of coronavirus infections in the United States are officially reported

According to a new model produced by Columbia University Mailman School of Public Health researchers, around one in three Americans had been infected with SARS-CoV-2 by the end of 2020. Simulating viral transmission across the whole country, the research suggests the number of officially confirmed cases can only account for a small volume of total infections.

“The vast majority of infectious were not accounted for by the number of confirmed cases,” explains Jeffrey Shaman, one of the researchers working on the study. “It is these undocumented cases, which are often mild or asymptomatic infectious, that allow the virus to spread quickly through the broader population.”

The research collected confirmed COVID-19 case data from 3,142 counties in the US and simulated transmission of the coronavirus across the country in 2020. The model estimated 103 million Americans had been infected with SARS-CoV-2 by December 31, 2020. This accounts for about 31 percent of the total US population.

Overall, confirmed cases only accounted for 22 percent of the total number of infections. This number is almost exactly the same as ongoing estimates from the Centers for Disease Control and Prevention (CDC). The CDC’s surveillance estimates less than a quarter of all SARS-CoV-2 infections in the United States are reported.

Infection rates across the US varied wildly depending on the time of year. Los Angeles County, for example, was estimated to harbor stunningly high infection rates at the very end of 2020, with 2.42 percent of its total population potentially contagious with SARS-CoV-2 on December 31st, whereas Miami experienced its infection rate peak in July when it was estimated 1.25 percent of the total population were infected.

Tracking fatality rates across 2020 the new research calculated a significant drop in COVID-19 mortality from spring to winter. During the pandemic’s initial wave the model estimated 0.8 percent of people died from COVID-19. However, by the end of the year this rate had fallen to just 0.3 percent. The drop in fatality rate is thought to be due to improvements in public health measures, such as mask mandates and better testing, and growing knowledge of how best to treat this new disease.

Despite the significantly high population infection rates in 2020, the researchers indicate 2021 presents an entirely different landscape for the pandemic. Of course, there are still millions of Americans yet to directly encounter the virus and susceptible to infection, and vaccinations will help prevent severe COVID-19 and death despite growing numbers of mild breakthrough infections, but a trio of fundamental factors is set to shape the pandemic over the course of the rest of this year, according to the new study.

“… our model does not represent re-infection, either through waning immunity or immune escape; however, re-infection has been documented, evidence of waning antibody levels exists, and new variants of concern have emerged and will likely continue to do so,” the researchers conclude in the newly published study. “All these processes will affect population susceptibility over time and help determine when society enters a post-pandemic phase.”

The new study was published in the journal Nature.

Source: Columbia University Mailman School of Public Health

4 comments
4 comments
Daishi
Between 1/3 of the people already having COVID and the number of people vaccinated you would think we would have some amount of herd immunity to slow down Delta but it's still really contagious.
Spud Murphy
If these numbers are true, and given the average death rate of around 2.2%, and the fact that obese people are more likely to die, so the death rate in the US would be higher, especially with their dodgy health care system, then the official death count is obviously off by at least a factor of 3, probably closer to 5 or more.
piperTom
IN the "initial wave the model estimated 0.8 percent of people died from COVID-19." What People? Confirmed infections or ALL people?! 0.8% of US population is over 2.6 million, yet the official death toll as today is 654,381. SO... confirmed cases?
There's a claim that the observed "drop in fatality rate is thought to be due to improvements in public health measures, such as mask mandates." I'd like to see the reasoning that a mask lets you catch it, it's going to be much less severe.
Daishi
@piperTom One reason is that the severity of your symptoms are dosage dependent on the amount of viral load. In theory if you are wearing a mask, socially distant, and avoided crowded poorly ventilated indoor areas if you still manage to get infected you would do so with a lower viral load than if you were not observing best practices. This isn't just hypothetical either as Delta is known to carry a significantly higher viral load than the original variant which contributes to it being both 1) more contagious and 2) more lethal. I hope that's useful information.