By Michela Reinink
Someone’s level of susceptibility to infectious diseases can be dictated by their genetic composition. A recent twin study from King’s College London has reported that 50% of the differences COVID-19 symptoms appear to be determined by genetic factors. Note that this study is not peer-reviewed, so cannot yet be regarded as established information. Nonetheless, the conclusions are interesting and warrant further study.
The results from this study could be used to explain why some people who contract COVID-19 experience severe symptoms requiring hospitalization, whilst others never experience any symptoms at all. This study shows that the symptoms of the virus, which differ greatly from person to person, are not random, but based partially on innate factors in addition to where you live and who you interact with.
The research used TwinsUK volunteers (n=2633) and the COVID-19 Symptom Tracker app to determine symptom heritability. This app allows members of the public to record their symptoms, and has over 2.7 million users, many of whom have been tested for the virus. Subjects are asked daily to log information on the presence or absence of symptoms into the app.
Twin studies are very useful in determining the role of genetics, as identical twins share 100% of their genes with each other, while non identical twins share only 50%. In this study, both identical and non-identical twins were studied. The rationale was that if COVID-19 symptoms are determined by genetic factors, there would be a greater similarity between identical twins compared to non-identical twins. This discrepancy between identical and non-identical twins was seen in the study.
Environmental factors, such as whether the twins shared a household or not, were adjusted for in relevant cases. A substantial genetic component was found to influence the following symptoms: loss of smell and taste, delirium, diarrhoea, and fever. However, symptoms such as cough, chest pain, and abdominal pain were not linked to genetic factors.
Understanding the role genetics play in COVID-19 could be useful in the development of drugs for the disease. Knowledge of how the virus passes through the population may aid in the discovery of the pathogenic mechanism of COVID-19. Also, identifying whether a person’s genetic composition puts them at higher risk would facilitate better protection for high-risk individuals.
Overall, this study provides interesting data on the heritability of COVID-19, but would benefit from peer-review and addressing the drawbacks of the study. Such shortcomings include a predominantly female sample largely consisting of people with European ancestry. Further genetic work is currently underway to determine which genes predict the severity of symptoms.