New data from medical records in Los Angeles indicate COVID-19 may have been circulating in the United States even before China informed the World Health Organization of the first outbreak of the then-unidentified virus, according to researchers at UCLA and the University of Washington.
In a study published Thursday in the Journal of Medical Internet Research, the team of nine researchers compared electronic medical records in the UCLA Health system from this winter to the previous five years and found an excess number of outpatient and emergency room visits with complaints of a “cough,” as well as hospitalizations for acute respiratory failure, beginning the week of Dec. 22, 2019.
From then through the end of February — a 10-week span — they estimated there were 1,047 more outpatient visits, 514 more emergency department visits and 387 more hospitalizations than their model would have anticipated, suggesting “community spread of SARS-CoV-2 prior to established clinical awareness and testing capabilities,” the researchers wrote.
The first confirmed case of the virus in the U.S. came Jan. 21, about three weeks after China first informed the WHO of what was then called “pneumonia of unknown cause.” It was revealed this spring that the first American death from the virus came much earlier than previously known, Feb. 6 in Santa Clara County, while other studies have suggested the virus was more widespread in the Bay Area than previously known.
However, there were no diagnostics tests performed on the UCLA patients, so it’s not possible to know the exact extent undiagnosed cases of COVID-19 explain the spike in the data.
“While asymptomatic transmission and community spread of COVID-19 are possible explanations for the observed excess patient encounters, other reasons and limitations need to be considered,” researchers wrote.
Some other reasons, researchers said, could be the early and especially strong peak of the 2019 flu season in Los Angeles, the mysterious vaping disease of 2019 or possibly more people seeking out medical advice for COVID-like symptoms once it gained media coverage in February.
The sheer prevalence of excess visits, based on modeling of past years’ flu seasons, led researchers to believe it could not be explained by the flu, while the vaping disease had subsided by that winter, according to the Centers for Disease Control and Prevention. The media was also an unlikely explanation because the coronavirus didn’t begin to garner serious attention in the U.S. until February, researchers said.
Even compared to the worst flu season of the past five years, researchers found there had been hundreds of more cases of “cough” being reported at clinic and emergency rooms around the city. In 2016-17, a total of 1,671 patients reported a cough in an outpatient visit, compared to 2,938 in 2019-20, though the raw figures don’t account for an overall increase in outpatient visits over that time.
Acute respiratory failure, a common symptom of COVID-19, also increased in hospital patients from the worst of the previous five years, even though overall hospitalizations decreased. From December 2018 through February 2019, there were 10,646 total hospitalizations, including 996 for acute respiratory failure. In the same period of 2019-20, the number of patients with acute respiratory failure increased to 1,138 even while overall hospitalizations fell to 9,903.
“It is possible that some of this excess represents early COVID-19 disease,” the researchers wrote.
They set out to identify previously uncovered cases of the virus using millions of electronic health records, which they said were underutilized in studying epidemiological trends. The UCLA Health system provided them records of 9.5 million outpatient visits, 575,000 emergency department visits and nearly 250,000 hospital admissions from January 2014 through February 2020.
Researchers used data from the previous five years to determine a seasonal average for December through February, then compared it to this year’s data to see how many excess visits there were outside a 95% interval of what was expected for that period.
They looked at 13 weeks of data, from the beginning of December to the end of February.
There was no increase in the first three weeks of December, but beginning the week of Dec. 22, the number of outpatient reports of cough symptoms was above that interval for all of the next 10 weeks. Emergency room visits were above that interval in six of those 10 weeks, while hospitalizations were above it for seven of them.
“A unique feature of this study is the evaluation of three different stages of health care settings,” researchers wrote. “Data from the outpatient clinic setting is usually a harbinger of what is to come for hospital emergency departments and intensive care units.”
While their methodology, which centered around searching for the word “cough” under the reason for visit in electronic medical records, may seem imprecise, researchers said its flaw was not casting a wide enough net, due to the wide variety of symptoms in COVID-19 patients.
“Although the term ‘cough’ is possibly more specific to COVID-19 than other symptoms such as ‘fever’ or ‘aches,’ this search method has imperfect specificity and sensitivity as it does not include the full spectrum of COVID-19 symptoms,” the researchers wrote.
The study would not capture any asymptomatic patients, who are said to account for as many as 40% of total cases, and only represents a picture of a singular medical medical system.
