Up to 60 percent of all COVID-19 cases in the United States may not have been counted, a new study finds.
Researchers at the University of Washington used test data, cases and death rates to estimate how many infections were likely missed in each individual US state.
The main reason for missed COVID-19 cases is the lack of available tests, reluctance to get tested for some – whether they have travel anxiety or don’t think their case was serious enough – or in some cases failures of the tests themselves.
This means that the actual number of infections could be around 86 million instead of 34.4 million, according to data from Johns Hopkins.
The team says a better understanding of the number of people who have contracted the virus will help manage the potential long-term effects the virus has on some patients.
Only one in 2.3 cases of COVID-19 were detected nationwide, according to a new study, meaning 60% of cases across the country went undetected
60% of COVID cases in Indiana went undetected, and many went undetected early in the pandemic
“There are all kinds of different data sources we can draw on to understand the COVID-19 pandemic — the number of hospitalizations in a state, or the number of tests that come back positive,” said senior author Dr Adrian Raftery, a UW professor of sociology and statistics.
‘But each data source has its own flaws that would give a distorted picture of what is really going on.
“What we wanted to do is develop a framework that corrects the flaws in multiple data sources and leverages their strengths to give us an idea of the prevalence of COVID-19 in a region, a state, or the country as a whole.”
Raftrey worked with Nicholas Irons, a doctoral student in Washington, to collect data on COVID cases, deaths and tests conducted in each state from March 2020 to March 2021.
They then used Indiana and Ohio as “anchors” for their study, as the states used some randomized tests during the pandemic.
In Indiana, they believe that one in 2.3 COVID cases – or just 40 percent – were detected, less than half.
However, that margin largely comes from the early months of the pandemic.
During the first two months of the pandemic, Indiana experienced the first major wave of the pandemic.
At the time, testing was limited and many pandemic-related social distancing and masking mandates were limited.
60% of COVID cases in Ohio went undetected, and many went undetected early in the pandemic
The same number of cases were discovered in Ohio – one in every 2.3.
The trends are also nearly identical, as a vast majority of cases went undetected at the start of the pandemic, but the proportion of undetected cases declined rapidly as testing became more widely available.
Data from the two states and the fact that their trends were so similar gave the team a foundation to build the rest of their research on.
In Connecticut and New York, two other states the researchers highlighted, about half — or one in two — COVID cases were detected.
Virginia was the most successful state, detecting one in 1.2 cases, or 83 percent.
The least successful was Idaho, where only 25 percent of cases were detected in the state, according to the model.
Researchers also found that one in 2.3 — or just 40 percent — of COVID cases were found nationwide.
This means that the number of actual cases in the US could reach 86 million – compared to the official number of 34.4 million cases.
The researchers believe their findings affect levels of herd immunity in the US.
Experts believe that at least 80 percent of the population must have COVID-19 antibodies for the nation to achieve herd immunity.
While there is some debate about how much natural antibodies protect a person from the virus, there is at least minimal immunity a person has after having the virus.
If the number of people with natural antibodies is 60 percent higher than expected, America could be closer to herd immunity than it seems.
It also means that the number of Americans with long-term COVID symptoms such as myocarditis – heart inflammation – anosmia and possible cognitive problems may be higher than expected.