Why some people have no complications from COVID-19, while some need critical intensive care?

Majority of those infected with SARS-CoV-2 (the virus causing COVID-19) show no symptom or only mild symptoms. A quarantine period of 14 days was used by most stakeholders in healthcare to reduce transmission as the incubation period may range from one to 14 days.

Once the body get infected with the virus, antibodies will be produced to fight the foreign substance ‘virus’ in order to eliminate it from the body. According to the recent study, the antibodies may last for only two to three months and asymptomatic patients may have a weaker immune response to SARS-CoV-2 infection compared to patients who develop symptoms.1

Is it because of the genetic variants?

Could different blood type cause different responses to the infection? To date, the answer is still ambiguous. However, a study suggests that the answer could lie in the DNA, the genetic variants that passed from our ancestors.

In a recent genome-wide association study (GWAS), it was found that genetic variants in two regions of DNA are linked to the severity of COVID-19 symptoms.2 Six genes including SLC6A20, LZTFL1, CCR9, FYCO1, CXCR6 and XCR1 genes are associated also with COVID-19.2 One of the gene, SLC6A20, is expressed in kidney and they encode for the amino acid transporter that interacts with angiotensin-converting enzyme 2 (ACE2). ACE2 is the main receptors for SARS-CoV-2 to get into the human cells.2 This might be the reasons why people with certain genetic variant may have more severe symptoms.

An initiative called Caronagenes has also been launched by The University of Edinburgh with the aim of using genetics to understand the symptoms and severity of COVID-19 (https://www.ed.ac.uk/coronagenes). Volunteers can contribute their DNA data to the initiative and help fight COVID-19.

 

References:

  1. Long, Q., Tang, X., Shi, Q. et al. (May, 2020). Clinical and immunological assessment of asymptomatic SARS-CoV-2 infections. Nature Medicine. Retrieved from https://doi.org/10.1038/s41591-020-0965-6
  2. Ellinghaus, D., Degenhardt, F., Bujanda, L., Buti, M., Albillos, A., Invernizzi, P., . . . Karlsen, T. H. (2020). Genome wide Association Study of Severe COVID-19 with Respiratory Failure. New England Journal of Medicine. doi:10.1056/nejmoa2020283
  3. Caronagenes. (June, 2020). The University of Edinburgh, United Kingdom. Retrieved from https://www.ed.ac.uk/coronagenes

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