Why does the SARS-CoV-2 virus seem to affect Black and South Asian Ethnic Groups more in the UK?
An interesting correspondence by Marion Cook in The Lancet July 17 suggests that this could be related to sickle cell and thalassaemia.
Sickle cell anaemia is an inherited autosomal recessive disease with homozygotes having sickle cell disease and heterozygous carriers having sickle cell trait. Sickle cell trait is asymptomatic. However, it is occasionally associated with sudden death induced by severe hypoxia. Hypoxaemia is a complication of COVID-19.
Another complication of COVID-19 is pulmonary embolism. It is known that pulmonary embolism is a severe clinical feature of COVID-19. People who have sickle cell trait have twice the risk of pulmonary embolism compared with the general population.
The relative frequency of sickle cell trait is higher in the black ethnic group than in the white ethnic majority in the United Kingdom. Interestingly, the black African ethnic group has twice the number of fatalities and frequency of sickle cell trait as does the black Caribbean group.
Beta-thalassaemia is inherited in an autosomal recessive manner with heterozygous carriers having beta-thalassaemia trait. Beta-thalassaemia is higher in the south Asian ethnic group than in the white ethnic majority. The only known symptom of beta-thalassaemia trait is a tendency for mild anaemia, which would aggravate hypoxaemia due to COVID-19.
Interestingly, the white Irish minority had half the number of fatalities as the white British majority. Haemochromatosis type 1 is higher in prevalence within the white Irish ethnic group than within the white British ethnic group. It is suggested that this could have an effect here.
The mutation C282Y is inherited in an autosomal recessive pattern. People with the C282Y allele are less likely than those without to be anaemic, homozygotes sometimes having to be regularly bled to reduce their iron overload. Iron-deficiency anaemia could aggravate hypoxaemia due to COVID-19. The prevalence of iron deficiency anaemia has been reported to be lower in white Irish than in white British men.
Marion Cook suggests that this data highlights the potential hypoxic effect of anaemia in COVID-19 fatalities for sickle cell anaemia carriers and for beta-thalassaemia carriers. They also indicate that haemochromatosis type 1 might confer some protection.
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