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Feature Christmas 2017: All Creatures Great and Small

The science behind “man flu”

BMJ 2017; 359 doi: (Published 11 December 2017) Cite this as: BMJ 2017;359:j5560

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Iron Man Flu

While not condoning the timbre of the subtitle, Professor Kyle raises an important point as to how sex differences may influence the manifestation of common conditions(1). However in her well-written and admittedly amusing piece there is possibly excessive focus on the reproductive hormones. Sex differences in iron levels may account for the apparently disparate natural history of influenza infection between men and women. Men generally have significantly higher levels of iron, in all its biological guises, than women(2). This potentially renders them more susceptible to influenza infections, which in themsevles may engender higher viral loads due to increased iron availability and thus produce more severe symptoms. Host iron sequestration is germane to the survival and life cycle of influenza viruses(3,4,5). Indeed a recognised virulence factor involves the influenza virus inciting macrophages to engult red blood cells thus supplying the intracellular pathogen with haem iron(4,5). Biochemically withholding and concealing iron from invading pathogens is a means of antimicrobial host defence(4). The greater abundance of iron in men may facillate viral colonisation and increase the alacrity of pathogen replication and invasion potentially eliciting more severe symptoms in men.

1. Sue K. The science behind "man flu". BMJ. 2017 Dec 11;359:j5560.

2. Kelly AU, McSorley ST, Patel P, Talwar D. Interpreting iron studies. BMJ. 2017 Jun 15;357:j2513. d

3.Drakesmith H, Prentice A. Viral infection and iron metabolism. Nat Rev Microbiol. 2008 Jul;6(7):541-52

4.Johnson EE, Wessling-Resnick M.Microbes Infect. Iron metabolism and the innate immune response to infection. 2012;14:207-16

5. Silva-Herzog E, Detweiler CS. Intracellular microbes and haemophagocytosis. Cell Microbiol. 2008;10:2151-8

Competing interests: No competing interests

03 January 2018
Chika Uzoigwe
Luis Carlos Sanchez Franco, Mohamed Wasfi, Omer Ali
Harcourt House, Sheffield
Harcourt House, Sheffield