Genetics

Who is at higher risk?

Scientists have not yet found out why some get very sick with COVID-19 and others have mild or no symptoms at all. There is evidence that chronic health conditions such as hypertension and diabetes can play a role but also genes can influence how bodies react to a virus.

A set of 68 genes have been identified and associated with a high risk of developing severe COVID-19. An Oxford-based analytics company PrecisionLife released a pre-print paper with this information in late June, they analysed the genomes of 929 patients from the UK Biobank who experienced severe symptoms to COVID-19.

Those using Genome Wide Association Studies, where they scan multiple genomes of individuals with a trait in hopes of finding common variants which may be associated with a that trait, came across a number of different problems. Studies had been limited by the heterogenous nature of COVID-19 (where it has a diverse range of symptoms ranging from very mild to severe) making it difficult to find common genes.

The PrecisionLife study overcame this barrier by evaluating combinations of genetic features, which is not possible with existing GWAS approach. They identified 12 of the 68 genes that are involved in blood circulation and the heart, including calcium level regulation, and this is consistent with the observation that the cardiovascular system will undergo severe stress in hospitalised patients suffering from COVID-19.

An international academic team when looking at 1,600 patients in Italy and Spain, found 2 areas of human DNA that differed significantly between those who had respiratory failure and those who had no signs of the disease at all:

One was a set of genes that will determine blood group - this may also have an impact on the severity of the disease (see Demographics - Blood Group) and the research found that individuals with group A blood are at higher risk of serious illness than those with group O.

The second covers genes involved the ACE2 receptor which SARS COV-2 uses to get into the cells.

By identifying the genes which make the disease worse in certain people personalised treatments for COVID-19 could be developed and those who could be more at risk could be identified.

Two international consortiums have been formed to coordinate further research, one in Finland and one in the US which is looking for variations in singles genes that would account for unusual cases of the young and healthy who have a life threatening response to the virus and also those who seem to resist infection.

Scientists are using human DNA in different ways to look into the disease with some using databases of genetic data that already exists and matching against COVID-19 patients and others starting with new genomes from COVID-19 patients. There are also different levels of analysis from whole genome sequencing to genotyping which is faster and cheaper.