US researchers have also estimated that the nation is substantially underreporting cases.
Coronavirus deaths across 25 states could be up to 40% higher, while total fatalities could be twice the current count in some states.
The coronavirus pandemic has exposed severe limitations in collecting data during a crisis.
In many countries, limited testing capacity and the difficulty of finding and identifying asymptomatic cases has likely caused many patients to go undiagnosed. COVID-19 tests can also produce false negatives if they aren't administered properly or if a patient isn't shedding enough virus to be detected in a sample.
Some public-health experts have suggested that the actual case totals in Italy and the US could be at least 10 times higher than the current figures. Death counts are likely to be inaccurately low as well.
"There are a lot of deaths that we probably will never know if they were coronavirus deaths or not," Elizabeth Halloran, a biostatistician at Fred Hutchinson Cancer Research Center and University of Washington, told Business Insider. "There could be a lot more people infected than we thought."
Data from the Italian research group Istituto Cattaneo now suggests that the number of coronavirus deaths in Italy was almost double the total reported by the Italian Department of Civil Protection as of April 1.
Data from the US is less complete, but many states have reported spikes in excess deaths that have yet to be attributed to the virus, suggesting that the actual number of coronavirus deaths could be around 30% higher. In some states, total fatalities could be twice the current count.
Italian provinces substantially underreported their outbreaks
To quantify the true number of fatalities in Italy, the Istituto Cattaneo compared the number of reported deaths from February 21 to March 21 to the average number of deaths during that same time period from 2015 to 2019.
According to data from the Italian Department of Civil Protection, Italy saw around 4,800 coronavirus deaths across more than 1,000 municipalities from February to March. But in total, these municipalities recorded 8,700 deaths outside the normal average — meaning thousands of excess deaths have yet to be explained.
In Lombardy, the northern region where Italy's first case was reported, the number of recorded deaths was more than double the average from the past five years. A case study from the Institute of Public Health Berlin and the Italian healthcare network Centro Medico Santagostino corroborates that finding. The research found that only half the deaths reported in Nembro — a municipality in Lombardy — from February 21 to April 11 were categorized as COVID-19 deaths. Yet in March, the municipality saw more deaths than in any single year since 2012; the death count that month was 15 times higher than the monthly average between January 2012 and February 2020.
"Reporting of confirmed COVID-19 specific deaths represents, at least for some Italian regions, a substantial underestimation of the actual number of deaths from the disease," the researchers wrote.
Other northern regions, like Emilia-Romagna, Trentino-Alto Adige, and Piedmont, saw their death counts rise by more than 50%, the Istituto Cattaneo found.
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Even southern regions outside the epicenter of Italy's crisis saw higher-than-average death counts from February to March. The researchers said one explanation for this could be that many coronavirus deaths occurred in people's homes, and therefore weren't included in the official case counts.
"The impact of coronavirus has spread widely across the Italian population," they wrote. "Substantial increases in mortality are also visible in areas other than those traditionally indicated as coronavirus hotspots."
The study ultimately concluded that Italy's true coronavirus death toll is nearly double the reported one. Officially, more than 31,000 people have died of COVID-19 in Italy.
US states reported an excess of unexplained deaths this spring
Though it's possible for some flu deaths to be mistakenly identified as the coronavirus, researchers at Harvard and Emory Universities found that the coronavirus has been far deadlier than the flu in terms of reported cases so far. In a new study, they compared the weekly death count for the coronavirus to weekly death counts for seasonal influenza in the US.
"Although officials may say that SARS-CoV-2 is 'just another flu,' this is not true," the researchers wrote. "The demand on hospital resources during the COVID-19 crisis has not occurred before in the US, even during the worst of influenza seasons."
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During the week ending April 21, the study found, the number of reported coronavirus deaths was 20 times higher than influenza deaths reported during the deadliest week of flu season (over a seven-year average). Based on this analysis, the researchers concluded that the current number of COVID-19 deaths might "substantially understate" the actual number of fatalities.
"As the CDC continues to revise its COVID-19 counts to account for delays in reporting, the ratio of counted COVID-19 deaths to influenza deaths is likely to increase," they wrote.
Across many states, the number of reported coronavirus deaths from mid-March through mid-April exceeded the number of typically recorded deaths from all causes during that time frame, a New York Times analysis recently found. Data from 25 states suggests only 40,000 of 55,000 excess deaths have been attributed to the coronavirus so far.
In New Jersey, only half of the excess deaths have been attributed to the coronavirus, suggesting that actual COVID-19 fatalities could be twice as high. The same goes for Colorado, Michigan, and Virginia.
Halloran said some of those unexplained deaths may never factor into the official count.
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