A recent study has found that host factors seem to influence the disease outcomes in COVID-19 patients more than viral genetic differences. The researchers from Shanghai examined clinical, molecular and immunological data from more than 300 patients confirmed with COVID-19.
The infection of SARS-CoV-2 can present, in some patients, as mild pneumonia, whereas in others it can lead to severe respiratory disease and death. The study, published yesterday in Nature, discovered two different SARS-CoV-2 strains within their patient cohort but found that viral variations did not significantly affect the patient outcomes. However, the host having a low level of lymphocytes appeared to predict severity.
Hongzhou Lu and his colleagues from Fudan University said in their paper that “the determinants of disease severity seemed to stem mostly from host factors such as age, lymphocytopenia and its associated cytokine storm, whereas viral genetic variation did not significantly affect the outcomes”.
To conduct this study the researchers analysed data from 326 individuals, of which five were asymptomatic (no fever, respiratory symptoms, or radiological evidence of the disease). However, most of the cohort (293 patients), had mild disease defined as having a fever and radiological evidence of pneumonia. 12 patients had severe disease and shortness of breath, and 16 had developed to a critical state that required a ventilator. As of the beginning of April, most of the patients had been discharged but six had died.
The researchers compared the viral genome data from 112 samples from patients in Shanghai to those reported in Wuhan and found 66 synonymous and 103 non-synonymous variants in nine protein-coding regions. The researchers then conducted a phylogenetic analysis of their samples and found no statistical differences in disease severity, lymphocyte count or viral shedding duration.
Meanwhile, the host factors appeared to influence severity, with leukocytopenia being more common among the severe and critically ill patients. They added that age, pre-existing conditions and gender also influenced disease severity.