Gaps in Early COVID-19 Data Contributed to Surge in US Cases

August 25, 2020 - Gaps in early COVID-19 data led to significant underreporting of coronavirus cases, ultimately contributing to a large number of infections in the US by early March, a study published in the Proceedings of the National Academy of Sciences revealed.

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While awareness and concern over COVID-19 grew in the US from January to March, it wasn’t until February 29th that Washington became the first state to declare a state of emergency, researchers noted.

Although several states had followed by mid-March, but a lack of a coordinated national response created a number of variables as each state decided how to react to an increasing number of cases.

A team from the University of Notre Dame used a simulation model beginning on January 1, 2020, using data reported by Johns Hopkins University on confirmed cases and deaths – accounting for asymptomatic infections, case fatality rates, and local transmission.

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Researchers first generated an estimate of total infections in the US through March 12. The team then factored in how detection of symptomatic infections changed over time and estimated the number of unobserved infections during this time.

The group estimates that more than 100,000 people were already infected with COVID-19 by early March, when only 1,514 cases and 39 deaths had been officially reported and before a national emergency was declared.

“We weren’t testing enough,” said Alex Perkins, associate professor in the Department of Biological Sciences, an expert in infectious disease epidemiology and population biology and the lead of the study.

“The number of unobserved infections appears to be due to very low rates of case detection during a critical time, when the epidemic was really starting to take hold in this country. Part of it was the availability of testing, but another huge part was case definitions and the fact that they were overly restrictive early on.”

According to the CDC, the first confirmed case of COVID-19 in the US was reported in January. Early guidance on identifying possible infection included respiratory symptoms, and travel to Wuhan, China, where an outbreak occurred in December 2019.

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“While we were focusing on people coming back from China, we were ignoring people coming from Europe, and actually quite a bit of the initial seeding of the virus into various parts of the United States came from Italy,” Perkins said.

By focusing the analysis on the January to March timeframe, when little to no action had been taken on a wide scale, researchers were able to incorporate a constant into their models.

While other studies offer a sense of how school closures and lockdowns slowed the spread of the virus, examining transmission during the first three months of the year offered epidemiologists a clearer picture of how the virus emerged and spread throughout the US so quickly.

“It was such a crucial period in terms of how this situation started. We look at the United States now and compare it to other countries like South Korea or Germany, New Zealand or Vietnam, any number of countries who have done a much, much better job controlling transmission. The key differences really come down to the time period we examine in this study,” said Perkins.

“Those countries had adequate surveillance up and running at that time, whereas we show that throughout most of February the United States missed the vast majority of infections that were already out there. This particular timeframe that we focus on is really important for figuring out how we got here in the first place.”

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A significant feature of the analysis is the model’s incorporation of many uncertainties that played out in the early days of the pandemic in the US. The number of unobserved and unreported infections also speaks to how critical containment strategies are when battling infectious diseases.

The potential for misdiagnosis and the limitations of surveillance are huge issues across infectious diseases, especially emerging infectious diseases, researchers stated. While public health officials have to act quickly to understand how a new virus functions, without appropriate testing or coordinated response strategies, the risk increases for infections to go unreported.

“I think the fact that there were so many infections by the second half of February speaks to the importance of and what we could have done in terms of containment. If you think about Ebola or SARS (severe acute respiratory syndrome) or other emerging infectious diseases, there have been cases that show up in the US or other countries where officials move quickly to get ahead of them,” Perkins said.

“They isolate those people, they do contact tracing — and transmission is extinguished. I think a lot of us were hoping that would be the situation with this disease. By the time we got to February, the problem had grown so big, containing the virus wasn’t possible.”