A study by Stanford University released today indicates the actual infection rate for the coronavirus is 50-85 fold higher than what is currently accepted by most estimates. Their random testing of 3300 residents of Santa Clara County demonstrates the coronavirus is extremely widespread.
This may seem like bad news on the surface, but it is actually very positive news on two fronts. First, it demonstrates that many Americans have been infected and either never presented symptoms or presented symptoms mild enough to prevent them from seeking medical attention. It was previously known that some carriers of the coronavirus never get sick at all, but this study shows the number is much higher than previous estimates.
More importantly, it shows the mortality rate from infection is much, much lower than other studies have indicated. According to this comprehensive study by one of the leading medical labs in the nation, the mortality rate for infection of COVID-19 is on par with or even lower than that of the flu.
The reason this study’s results deviate widely from others is because it took a large, random sampling of residents. Other studies have focused on those showing symptoms, prompting the much higher mortality rate estimates. But Stanford’s study demonstrates the vast majority of people who are infected with the coronavirus never even show major symptoms, if at all.
Background
Addressing COVID-19 is a pressing health and social concern. To date, many epidemic projections and
policies addressing COVID-19 have been designed without seroprevalence data to inform epidemic
parameters. We measured the seroprevalence of antibodies to SARS-CoV-2 in Santa Clara County.Methods
On 4/3-4/4, 2020, we tested county residents for antibodies to SARS-CoV-2 using a lateral flow
immunoassay. Participants were recruited using Facebook ads targeting a representative sample of the
county by demographic and geographic characteristics. We report the prevalence of antibodies to SARSCoV-2 in a sample of 3,330 people, adjusting for zip code, sex, and race/ethnicity. We also adjust for test
performance characteristics using 3 different estimates: (i) the test manufacturer’s data, (ii) a sample of 37
positive and 30 negative controls tested at Stanford, and (iii) a combination of both.Results
The unadjusted prevalence of antibodies to SARS-CoV-2 in Santa Clara County was 1.5% (exact
binomial 95CI 1.11-1.97%), and the population-weighted prevalence was 2.81% (95CI 2.24-3.37%).
Under the three scenarios for test performance characteristics, the population prevalence of COVID-19 in
Santa Clara ranged from 2.49% (95CI 1.80-3.17%) to 4.16% (2.58-5.70%). These prevalence estimates
represent a range between 48,000 and 81,000 people infected in Santa Clara County by early April, 50-
85-fold more than the number of confirmed cases.Conclusions
The population prevalence of SARS-CoV-2 antibodies in Santa Clara County implies that the infection is
much more widespread than indicated by the number of confirmed
If we use today’s confirmed deaths, 69, and the estimated numbers in the Stanford study from early April, the mortality rate is between 0.08% and 0.14%, or 8-14 deaths per 10,000 infected. That is a far cry from the 3.5% or higher rate currently being used, a number that would attribute 350 deaths per 10,000 infected.
BREAKING: Coronavirus random sampling study from Stanford. They found the infection is 50-85 x more common than previously thought & fatality rate accordingly 50-85 x lower than the crude numbers would suggest. #COVID-19 https://t.co/LWo4PTSjj0
— Lisa Boothe (@LisaMarieBoothe) April 17, 2020
This study is the first large-scale community-based prevalence study of its kind. They used serological tests to identify antibodies. “These prevalence estimates represent a range between 48,000 and 81,000 people infected in Santa Clara County by early April.”
— Lisa Boothe (@LisaMarieBoothe) April 17, 2020
Another interesting point from the study, "A hundred deaths out of 48,000-81,000 infections
corresponds to an infection fatality rate of 0.12-0.2%."— Lisa Boothe (@LisaMarieBoothe) April 17, 2020
Having exponentially more infections may sound like bad news, but it’s actually extremely good news. It means millions of Americans have likely been infected and beat the coronavirus without knowing they had it. It also means mortality rates are much, much lower.
