DETROIT, Mich. — While some health experts warn of a possible second wave in the coronavirus pandemic, a new study is pointing to signs that COVID-19’s severity may be fading. Researchers at Wayne State University say viral loads from patients are continuing to decrease as the pandemic progresses. This is also showing a connection to a lowering death rate.
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. 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 as a Ct of 25 and under, intermediate loads as a Ct between 26-36, and low viral loads as a Ct over 37.
Lower viral loads lead to better outcomes for COVID patients
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 however, 70 percent of positive COVID-19 swabs fall into the low VL category. El Zein adds that this drop in viral production coincides with a decrease in patient deaths. 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.
“During the April-June 2020 period of the COVID-19 pandemic, the initial SARS-CoV-2 load steadily declined among hospitalized patients with a corresponding decrease in the percent of deaths over time,” the Wayne State team says in a media release. “Though confounding variables have not been evaluated, this suggests an association between initial viral load and mortality.”
Face masks, social distancing still the keys
Dr. El Zein admits the team doesn’t know the exact reason why viral loads are dropping over time, but suggests the pandemic’s severity is fading since a global crisis was officially declared on March 11. Part of this, he adds, may be due to the public’s actions to curb the spread.
The findings were presented at the European Society of Clinical Microbiology and Infectious Diseases’ Conference on Coronavirus Disease.