Naked Science Forum
Life Sciences => Cells, Microbes & Viruses => Topic started by: James Creamer on 31/05/2008 10:44:59
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James Creamer asked the Naked Scientists:
I love your podcast (http://www.thenakedscientists.com/HTML/podcasts/)! I'm one of those OCD Fans that has listened to the entire back library.
Something caught my ear the other day, you listed off the years of known flu pandemics. I'm a genealogogist and checked those years against deaths in my family and managed to find not one death during those years. Does this mean that my ancestors were very lucky, or possibly does it indicate some sort of flu resistance?
Thanks for your time,
James Edward Creamer
Albuquerque NM, USA
What do you think?
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It could mean either James!
Throughout history we have been selecting genes on the basis of the resistance that they give us against different pathogens. The best described and most famous example is the discovery of people with a mutation in a gene called CCR5.
This encodes a cell surface chemokine receptor which is used by HIV to gain entry to white blood cells. When HIV began to bite in the homosexual population in the US cases began to emerge of people who had lost several partners to HIV but had not themselves succumbed to the disease or even been infected, despite almost certainly coming into contact with the virus regularly.
A careful study of these cases revealed that their CCR5 gene had a piece missing; this deletion was called CCR5-delta32. It provides carriers with resistance to HIV infection but does not in itself seem to adversely affect immune function.
Intriguingly, it's also much more common in the European population (i.e. communities who subsequently peopled countries like the US and Canada) than in Africans. This suggests that some sort of selective pressure has enriched this gene variant in the European population.
One theory is that the Black Death, which had been ascribed to bubonic plague bacteria - Yersinia pestis, was actually some sort of virulent haemorrhagic viral infection; some scientists think that CCR5-delta 32 might have had the same sort of protective effect against this earlier viral assault in the middle ages, which wiped out one third of Europe's population, thus accounting for the common presence of this gene now.
The same may be true for flu, but as yet we don't know enough about pandemics of influenza to accurately pinpoint who's at risk. That said, scientists are now beginning to look at DNA samples from patients who died of H1N1 to see if there are any genes that crop up more often than they do in the general population. If these genes do exist, perhaps your family doesn't possess them!
Chris
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I have a question with that then. If say the immunities for certain bacteria and viruses (like the bubonic plague) are in fact mutations in the genetic structure, and can be passed down from parent to child, then wouldn't we see large populations of people in certain countries who had survived, rather than the general death of a lot of people everywhere?