The shut down and lock downs of recent months have all been based on the premise that COVID-19 would kill more than 2 million Americans without taking some serious actions to slow down the spread of the virus, as we didn’t have any immunity to this novel disease. The model used at that time assumed the case fatality rates being at 1-3%, and at the time W.H.O estimated a case fatality rate of 3.4%.
Some experts are questioning these assumptions, arguing that without widespread accurate testing the known cases are likely to be only a very small portion of the true number of infections given the ease of spread, and thus high case fatality rate could be well off the mark by orders of magnitude. The truth is that we don’t know what portion of infections have gone undetected and probably since cleared in the vast majority of the population due to lack of testing, the highly restrictive qualifications to get tested, and the potentially large incidence of mild illness or asymptomatic infection to this highly contagious virus running amok since January at an unknown rate.
As the weeks pass more data is being released supporting these views such as a recent preliminary study from researchers at Stanford which conducted a seroprevalence study of Santa Clara County, California on April 3-4, 2020 studying a representative sampling of 3,300 residents to test for the presence of antibodies in their blood to show if they had previously been infected with COVID-19.
This study revealed that the Bay Area infections based on the antibody testing were 85 times higher than what had been reported, which is largely due to the lack of testing and asymptomatic carriers allowing the virus to spread unknown. The researchers suggest that their data may help to better estimate the true fatality rate of this virus; the population prevalence of COVID-19 in Santa Clara among the 3,300 adults and children ranged from 2.49% to 4.16%.
“The most important implication of these findings is that the number of infections is much greater than the reported number of cases,” the researchers wrote, in a yet-to-be peer-reviewed study. “Our data imply that, by April 1 (three days prior to the end of our survey) between 48,000 and 81,000 people had been infected in Santa Clara County. The reported number of confirmed positive cases in the county on April 1 was 956, 50-85-fold lower than the number of infections predicted by this study.”
“Many estimates of fatality rate use a ratio of deaths to lagged cases (because of duration from case confirmation to death), with an infections-to-cases ratio in the 1-5 fold range as an estimate of under-ascertainment,” the researchers wrote. “Our study suggests that adjustments for under-ascertainment may need to be much higher.”
Detecting previously unreported cases of COVID-19 infections could lead to a better estimation of the fatality rate. This study was not without limitations, but after adjustments were made to take these into account the researchers suggest these results could be applied to other areas.
“While our study was limited to Santa Clara County, it demonstrates the feasibility of seroprevalence surveys of population samples now, and in the future, to inform our understanding of this pandemic’s progression, project estimates of community vulnerability, and monitor infection fatality rates in different populations over time,” the researchers said. “It is also an important tool for reducing uncertainty about the state of the epidemic, which may have important public benefits.”
“This probably aligns with what overall national exposure may be, on order of about 5 percent once we do wide serology,” tweeted Dr. Scott Gottlieb, former FDA commissioner, agreeing that these findings likely align with what the overall national exposure may look like. “Santa Clara was a hot spot and I would have expected exposure to be higher. Overall we’re probably diagnosing 1 in 10 to 1 in 20 infections.”
Gottlieb also suggests that other hot zones such as New York that have reported over 223,000 cases of infection have data “to suggest the infection rate may be much higher.”
“We’re also likely to find higher rates of infection among certain jobs,” he tweeted. “But the data so far suggest that nationally, total exposure is still low.”
As several states begin to cautiously reopen there has been an increased push for antibody testing which, if accurate, may be able to reveal who already had the virus who may not have been tested for it. Antibody testing can be conducted via blood but can also be done using saliva looking to detect IgM and IgG antibodies that can take up to 14 days to develop.
“Those who test positive for immunity, in theory, are safe to return to work but it is to be very cautioned against doing so considering medical professionals are still learning about this virus,” said Dr. Robert Segal. “The human race has not developed an immunity to this virus, there is a possibility that re-infections could occur. We cannot be certain of that at this time.”
Accuracy of these rushed to market tests have however been called into question. As with any test accuracy is always a concern, and many of these rushed serology tests have yet to be approved by the FDA.
John Brownstein an epidemiologist at Boston Children’s Hospital said that there is growing recognition in the field that the numbers of those infected are far greater than the official numbers, and ultimately he says about this study that, “It adds to growing body of work that suggests a huge amount of cases that went undetected.”
