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Covid-19: a puzzle with many missing pieces

BMJ 2020; 368 doi: (Published 19 February 2020) Cite this as: BMJ 2020;368:m627

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Clinical findings in a group of patients infected with the 2019 novel coronavirus (SARS-Cov-2)

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Re: Covid-19: a puzzle with many missing pieces

Dear Editor

Covid-19: a puzzle with many missing pieces


Emerging pieces of the Covid-19 puzzle include:
Very strong gender bias
Strong age bias
An observed but unclear relationship with BCG
Chloroquine good, NSAIDs bad – both drugs with effects on immune function
Unexpected delay in spread of the epidemic in Africa

What connects these? A possibility that fits with the facts is that the lung pathology of severe Covid-19 infection is dependent on a strong Type IV cellular response, known to be a factor in men and in older people.

History and theory suggest a low Th1 activity in East African countries with a poor maize-based diet 1, where TB and measles have been common killers, and where kwashiorkor children were once described as having a nutritional thymectomy 2. The almost exclusive dominance of dietary omega-6 in a maize-based diet is a background to this.

Poverty of Th1 response may therefore have changed from liability to asset. This interpretation does not predict less infection, but does predict a reduction in severe lung pathology in countries with reduced Th1 immune competence – for example East, Central and Southern Africa.

The Veneto region of Italy has historically been a maize dependent area also, and while other good explanations have been offered, it is fascinating to see a much lower reported Covid-19 mortality rate there than in other parts of Italy where a ‘Mediterranean’ diet, containing much Omega-3, is normal.

It is perhaps too early to see the pattern clearly. Africa must hold its breath.

Alastair M Sammon
Honorary Professor of Human Biology
Walter Sisulu University, South Africa

1) Sammon AM. Dietary linoleic acid, immune inhibition and disease. Postgraduate Medical Journal. 1999; 75(881);129-132. DOI:10.1046/j1365-2168.1998.00780.x

2) Smythe PM, Schonland M, Brereton-Stiles GG et al. Thymolymphatic deficiency and depression of cell-mediated immunity in protein-calorie malnutrition. Lancet 1971; 2:939-944 DOI:10.1016/s0140-6736(71)90267-4

Competing interests: No competing interests

15 April 2020
Alastair M Sammon
Honorary Professor of Human Biology
Walter Sisulu University
Private bag X1, Mthatha, Eastern Cape, 5100 South Africa