A team of US researchers has uncovered genetic links between COVID-19 severity and certain medical conditions that are known risk factors for the severity of the infectious disease.

Some people with COVID experience the disease more severely than others, and previous research has identified certain variants in specific human genes that are associated with a person experiencing more severe COVID.

Some of these variants may also be associated with other medical conditions that may already be well understood, identifying these shared variants could improve understanding of COVID and illuminate potential new paths for treatment.

To identify shared variants, the team Corporal Michael Crescenz VA Medical Center in the US, used an unprecedented dataset of genotypic information linked to electronic health record data (EHR) for more than 650,000 US veterans.

The findings, published in the open-access journal PLOS Genetics, revealed that certain variants associated with COVID are also associated with known risk factors for COVID. Particularly strong links were found for variants associated with venous embolism and thrombosis, as well as Type 2 diabetes and ischemic heart disease - two known COVID risk factors.

Among respiratory conditions, idiopathic pulmonary fibrosis and chronic alveolar lung disease shared genetic links with severe COVID, but other respiratory infections and chronic obstructive pulmonary disease (COPD) did not.

Some variants, associated with severe COVID, were also associated with reduced risk of autoimmune conditions, such as psoriasis and lupus. These findings highlight the need to carefully weigh various aspects of the immune system when developing new treatments.

"One thing that stood out to us was the high number of immune-mediated conditions that shared genetic architecture with severe manifestations of COVID-19," said Katherine Liao from the Centre.

"The nature of the associations brought to light how the SARS-CoV2 virus pushes on a pressure point in the human immune system and its constant balancing act of fighting infection while maintaining enough control so that it does not also become an autoimmune process, attacking self," she added.