A new study has found signs that the severity of COVID-19 — and the viral loads those infected carry — may be fading.
Researchers at Wayne State University say that viral loads, which is the amount of the virus in a patient’s system, continue to drop, which could explain why the death rate is falling.
“Dr. Said El Zein and his team analyzed viral loads of SARS-CoV-2, the virus causing COVID-19, coming from patient nasal swabs over two months,” Study Finds reported on Sunday. “From April 4 to June 5, a downward trend in the amount of virus detected in patients at Detroit Medical Center was discovered.”
To estimate the viral loads coming from nasopharyngeal swabs, study authors use a cycle threshold (Ct) value that comes from the tests on these samples. A higher Ct means a sample has less SARS-CoV-2 in it. Their scale rates a high viral load [VL] as a Ct of 25 and under, intermediate loads as a Ct between 26-36, and low viral loads as a Ct over 37.
During the week of April 4, just under half (49%) of COVID-19 patients had an intermediate viral load (VL). Low and high VL counts both came in at 25.5 percent of the patient samples.
By the fifth week of the study, El Zein said, 70 percent of positive COVID-19 swabs fell into the low VL category. That, in turn, coincided with a decrease in patient deaths, the doctor said.
“Researchers say 45 percent of patients in the high VL group died from the virus. This number falls to 32 percent for COVID-19 patients with intermediate loads and 14 percent for the low VL group,” Study Finds reported.
There have been other reports about “viral loads.” The most used test to determine if someone has COVID-19, known as a PCR test, is either positive or negative, that’s it. But the test does not identify the viral load — the greater the amount of virus, the more likely it is that the patient is contagious or may get severely ill.
“In three sets of testing data that include cycle thresholds, compiled by officials in Massachusetts, New York and Nevada, up to 90 percent of people testing positive carried barely any virus,” The New York Times reported in August after conducting a review of data.
Apoorva Mandavilli, the Times reporter who wrote the piece, said on Twitter: “NEW: All these months into the pandemic, we may have been testing the wrong way. Data from some state labs suggest up to 90% (!!) of people who get a positive result are no longer contagious and don’t need to isolate.”
“It turns out that the PCR, that old reliable workhorse, is both too slow and too sensitive for what we need. And it all hinges on a metric called the ‘cycle threshold,’” she wrote in another post.
The current PCR test analyzes genetic matter from the virus using 37 or 40 cycles, but health experts say that is too high because it detects even small amounts of the virus that pose no risk of contagion.
“Tests with thresholds so high may detect not just live virus but also genetic fragments, leftovers from infection that pose no particular risk — akin to finding a hair in a room long after a person has left,” Dr. Michael Mina, an epidemiologist at the Harvard T.H. Chan School of Public Health, told the paper.