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A team of researchers in California has discovered that the number of coronavirus cases in a county can actually be up to 85 times higher than health officials have counted, and say their data can help better estimate the true death rate from the virus.
Earlier this month, Researchers led by Stanford University tested 3,330 adults and children in Santa Clara County, who were recruited using Facebook ads, for SARS-CoV-2 antibodies and found that the prevalence of the COVID-19 population in Santa Clara varied from 2.49% to 4.16%.
“The most important implication of these results is that the number of infections is much higher than the number of cases reported”, researchers wrote, in a study not yet peer reviewed. “Our data implies that as of April 1 (three days before the end of our survey) between 48,000 and 81,000 people had been infected in Santa Clara County. The number of confirmed positive cases reported in the county on April 1 was 956, 50 to 85 times less than the number of infectious cases predicted by this study. ”
Asymptomatic coronavirus carriers have long been a concern of health officials and those seeking to understand the prevalence of the virus. The researchers also concluded that detecting previously unreported coronavirus cases could also lead to a “best estimate of the COVID-19 mortality rate”.
“Many estimates of the mortality rate use a delayed death / case ratio (due to the time between confirmation of case and death), with an infection-case ratio in the range of 1 to 5 as an estimate of the sub-finding The researchers wrote. “Our study suggests that the adjustments for underreporting may need to be much higher.”
The researchers noted that the study had several limitations, including that participants had to have access to Facebook and a car to get to the driving test sites. These factors have led to an over-representation of white women aged 19 to 64 and an under-representation of the Hispanic and Asian populations.
However, once the adjustments were made, the researchers said the results could be applied to other areas.
“Although our study was limited to the county of Santa Clara, it demonstrates the feasibility of seroprevalence surveys of population samples now and in the future, to clarify our understanding of the progression of this pandemic, to project estimates of the vulnerability of the community and monitor mortality rates from infection in different populations over time, “said the researchers. “It is also an important tool to reduce uncertainty about the state of the epidemic, which can have significant benefits for the public.”
Dr. Scott Gottlieb, former FDA commissioner, agreed that the results were likely aligned with what the overall national exposure might look like.
“This probably corresponds to what the overall national exposure can be, around 5% once we have carried out a broad serology,” he tweeted on Friday. “Santa Clara was a hot spot and I expected higher exposure. Overall, we probably diagnose 1 in 10 to 1 in 20 infections. ”
Gottlieb tweeted that in other hot spots, such as New York, which has reported more than 223,000 cases of the virus, data “suggests that the infection rate could be much higher.”
“We are also likely to find higher infection rates in some jobs,” he tweeted. “But the data so far suggests that at the national level, total exposure is still low.”
As several regions in the county are cautiously starting to consider reopening their states, there has been increased pressure for generalized antibody tests that can reveal who has previously had the virus but has not been tested for it.
The antibody test, which is largely done via a blood sample but can also be done using saliva, seeks to detect two sets of antibodies called IgM and IgG. With the new coronavirus, it takes about 1 to 14 days for the body to develop antibodies, Dr. Robert Segal, co-founder of LabFinder.com told Fox News.
“Those who have a positive immunity test, in theory, can safely return to work, but one should be very careful not to do so, since healthcare professionals are always aware of this virus” said Segal. “The human race has not developed immunity against this virus, it is possible that re-infections may occur. We cannot be sure for the moment. “
However, as with all tests, accuracy remains an issue, said Segal. The Premier Biotech serological test, which was used in the Santa Clara County study, has not yet been approved by the FDA.