A 40-year-old Spanish man has been charged after allegedly intentionally spreading COVID-19 to his co-workers and fellow gym members. The man, whose name has not been revealed by police, is alleged to have stayed at his workplace and visited his gym, continuing “with his normal life,” after showing symptoms and returning a positive Polymerase Chain Reaction (PCR) test for the SARS-CoV-2 virus, according to a police press release.
The incident happened on the Mediterranean island of Mallorca, just prior to an outbreak at the company the man was working at, which police began investigating back in January.
Just days before the outbreak, when he was at work the man started to show potential symptoms of Coronavirus Disease 2019 (COVID-19), which led colleagues to encourage him to quarantine. He refused. After work, the man went to take a PCR test at a medical center. The next day, he continued his regular routine, attending work and the gym. His superiors told him to go home after he was found to have a temperature of 40C (104F), but he still refused.
Allegedly, the man then walked around his workplace with his face mask lowered, coughing and telling everyone, “I’m going to infect you all with the coronavirus.”
At the end of the day, his PCR test came back positive for SARS-CoV-2, arousing fear in his colleagues. Afterwards, five people at his workplace also tested positive, with family members, including three infants, also testing positive.
At the gym the man attended, three people tested positive, with family members also testing positive. Police say that in total, 22 people were found to have tested positive for SARS-CoV-2, and the man was directly responsible for the positive tests.
None who tested positive developed symptomatic infection requiring hospitalization. The individual was charged and released on April 24 and is now awaiting trial according to Spanish news source Europa Press.
PCR false positives a ‘significant problem’
According to ICD10Monitor, a website with a stated goal of catering to healthcare providers aiming to provide informed decisions, PCR testing has some significant caveats: “Medical and public health professionals have generally treated positive results from PCR-based tests for COVID-19 as if they are completely reliable,” says Andrew N. Cohen, PhD. “We’re told that if we test positive, then we are infected with the virus, and that positive results in PCR tests are rarely if ever inaccurate. In fact, however, false positives occur in PCR tests for COVID-19 often enough to be a significant problem.”
Cohen explains in layman’s terms how PCR testing is “a chemical reaction that repeatedly duplicates certain targeted segments of the virus’s RNA, until there’s enough of it to be detected. The targeted segments are carefully selected to be unique to the COVID-19 virus, and thus absent from other genetic material – human tissues or other pathogens – that might be present in human respiratory samples.”
Cohen warns that while the accuracy of PCR testing is rarely discussed in network media articles, there is a significant risk of producing false positives based on the Cycle Threshold (CT) tests are run with. “Because of the high degree of duplication of the targeted genetic segments by PCR tests (which, depending on the number of duplication cycles run, can multiply an initially low concentration of these segments by a billion times or more), trace amounts of contamination can produce false-positive results that are indistinguishable from true positive results.”
“Such minute levels of contamination can be extremely hard to control. False positives from contamination have been regularly documented in diagnostic PCR tests, including in the most highly regarded laboratories.”
While false positive rates are generally quite low, Cohen states that “when the rate of infection is low, even a small false-positive rate can greatly diminish the reliability of positive test results.” He bases his estimates on a comprehensive review of literature and real-world data. “When we began this work in March, no external quality assessments had yet been completed for COVID-19 PCR tests. So we reviewed 43 external quality assessments of PCR tests for other viruses similar to COVID-19, and found that half of these assessments produced false-positive rates between 0.8 and 4.0 percent, with a median value of 2.3 percent.”
“Since then, results have become available from a few external quality assessments of COVID-19 tests. These have false-positive rates ranging from under 0.4 to 0.7 percent…Our third line of evidence is from real-world uses of COVID-19 PCR tests wherein positive results were checked with additional tests. In most of these, the false-positive rate was between 0.2 and 0.9 percent.”
The article illustrates a theoretical example where 100,000 people are tested, “With 1 percent, or 1,000 of them, being infected. If the false-negative rate is 25 percent, a typical estimate from the scientific literature on COVID-19, and the false positive rate is 0.5 percent, a reasonable estimate from our data, then a quarter of the 1,000 samples from infected individuals – that is, 250 samples – will be false negatives, and the rest will be true positives.” Accordingly, there would be 750 true positives, or positive test results that are actually correct, out of 1,000 infected individuals.
On the other hand, with a false positive rate of 0.5 percent, there would be 495 false positive tests, or positive test results that are actually incorrect, out of 99,000 uninfected individuals. Dividing 495 false positives by the sum of false positives and true positives, or 495 divided by the sum of 495 and 750, equals 40 percent. “So, with a 1-percent infection rate in the test population, a false-positive rate of only 0.5 percent leads to nearly 40 percent of the positive results being wrong,” he says.
“And although the false-negative rate is 50 times higher than the false-positive rate, it is nevertheless much more likely (nearly 160 times more likely) that a positive result will be wrong than a negative result will be wrong.”
“Notice that this doesn’t align with what most health authorities have been telling us, which is that we can trust a positive PCR result as proof that we’re definitely infected, but that we can’t rely on a negative result as proof that we’re not infected. In fact, just the opposite is true – negative results are reliable and positive results are not – when the infection rate is low.”
Additional reporting by David Wagner and Neil Campbell