New research from Cleveland Clinic suggests that early mutations of the SARS-CoV-2 virus were deadlier but quickly overtaken by more transmissible variants, which may explain why mortality has decreased as the COVID-19 pandemic has progressed.
For the study, published April 26 in JAMA Network Open, researchers genetically sequenced virus specimens from 302 COVID-19 patients treated at Cleveland Clinic between March 11 and April 22, 2020. Researchers compared their findings to the original virus strain found in Wuhan, China, according to CIDRAP News.
They found 484 unique mutations from six different virus strains. Patients infected with earlier virus subgroups had a 21.4 percent risk of death, compared to just 5.6 percent for those infected with later strains.
Researchers found a rapid reduction in the diversity of virus subgroups by late March 2020, which may have been due to public health measures preventing new variants from entering the Cleveland community. As the pandemic went on, more transmissible variants associated with better hospital survival rates overtook early variants as the most dominant strains, they added.
"These findings help explain persistent hospitalization yet decreasing mortality as the pandemic progresses," the researchers said. "SARS-CoV-2 clade assignment is an important factor that may aid in estimating patient outcomes."
To view the full study, click here.