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Scientific responses to 3 common myths about COVID-19
Kyle Tretina, Ph.D.,
Genomics Application Scientist
Posted on July 8th, 2020
MYTH #1: COVID-19 is only about as deadly as the flu
One of the most common ways of measuring the deadliness of an infectious disease is the case fatality ratio (CFR), which is the number of confirmed deaths divided by the number of confirmed cases. What we really want to look at to answer this question, is the infection fatality rate (IFR), which uses the total number of deaths divided by the total number of cases. The main trouble in comparing COVID-19 to the flu is that the total number of cases of COVID-19 is not known and can only be estimated. Importantly, CFR is often very different from the IFR, and in the case of COVID-19, there is likely a vast underreporting of cases.
Accurately measuring the deadliness of COVID-19 is far more difficult than you might initially think, since it depends on the number of total cases and the number of deaths attributed to the infection. Each of these numbers is susceptible to biases associated with surveillance, data synthesis, diagnosis and reporting. When looking through the literature, you should note that any reported CFR should include information about the time frame and geographic location under consideration, since CFR can vary dramatically by country, region, population age, population sex ratio, as the response of a government evolves throughout a pandemic, and many other factors. Instead of diving into a discussion of how various countries report the data leading to their CFR, let’s look at the data from a few sources using selected countries where the data are believed to be of the best quality and see how they compare.
According to the European CDC, the COVID-19 CFR has changed significantly by country throughout the course of the pandemic, ranging from 1.4% (Australia) to 18.5% (France) (Figure 1). Some studies have tried to improve on this reporting methodology to account for potential underreporting and publication bias, estimating a global CFR of 7.4%. Another alternate method tried to capture the total number of cases more comprehensively by looking for SARS-CoV-2-reactive antibodies in various populations and estimated a CFR of 0.02% to 0.78% (median 0.25%). According to one of the most popular COVID-19 dashboards, as of 06/26/2020, there have been 9,682,414 cases of COVID-19 and 491,113 deaths, resulting which would correspond to a CFR of 5%. This is essentially identical to the COVID-19 CFR in the U.S.A. (124,749 deaths and 2,446,706 cases, CFR = 5%). For various technical reasons, many public health experts prefer measures other than CFR, such as case fatality risk (measures in deaths per 100,000 cases or infections). A CFR of 5% would correspond to a risk of 5,000 deaths per 100,000 cases.
Figure 1. The COVID-19 case fatality ratio of selected countries based on data from the European CDC.
Table 1. Selected viruses, viral diseases and their estimated case fatality ratios.
MYTH #2: Thermal scanners are enough to detect COVID-19
Many businesses are using only thermal scanners as a screening tool for worksite re-entry, but there are several problems with that approach. First, a recent study from the UK indicated that 71.5% of the 13,863 individuals testing COVID-19 positive indicated fever as a symptom, which means that ~30% of symptomatic positive cases would be missed if only fever is used as a screening tool. In addition, other research indicates that the time from exposure to the virus to symptoms can extend to 14 days, with a median time of 4–5 days. There is also an issue of sensitivity, as demonstrated by one study that found that self-reported fever had a sensitivity of 75.0% and a specificity 84.7%, indicating that even in cases where the person has a fever, a thermal scanner may not detect it. In all of these cases, thermal scanners will miss potentially infectious employees.
MYTH #3: COVID-19 is only dangerous to older people with underlying medical conditions
While people over age 85 are most likely to die from COVID-19, mortality rates for people age 55 and younger can still reach up to 4% and account for almost a quarter of total deaths in some places like New York City. Young people contribute a significant amount of transmission in endemic areas[22,23], but they may have hidden complications that don’t show as obvious symptoms that could be a problem later. This is a pattern that is only beginning to be described, but doctors are reporting that they are getting COVID-19 patients with very low blood oxygen saturation levels, but seem to be breathing well. Instead of the acute respiratory distress syndrome (ARDS) that typifies many older COVID-19 patients, they have reduced lung function, but don’t realize it yet. This finding simply underscores how little we know about the long-term effects of SARS-CoV-2 infection, even in asymptomatic cases.
Kyle has extensive research expertise and interest in the area of genomics, microbiology and immunology. He received his Ph.D. from the University of Maryland, Baltimore working at the Institute for Genome Sciences and came to Meenta from a postdoc at Yale University.