Wednesday, August 31, 2005

The Black Death

A book by Susan Scott and C. Duncan (ISBN 047090006) (Academics)

The main thrust of their argument is that the Black Death was a haemorrhagic viral disease , not Bubonic Plague . Their argument has convinced me .

In a neat bit of epidiomological detective work they deduce basic characteristics of the the virus from the raw data of English parish burial records.

The profile of the Black Death :

Latent Period from time of infection : 10 - 12 days
Infectious period (after latent period)before the appearance of symptoms : 20 - 22 days Incubation period before symptoms ( sum of above) : approx 32 days Average period displaying symptoms before death : 5 days Total infectious period : approx 22 + 5 = 27 days Time to death from infection : approx 37 days .

The long infectious period before the appearance of symptoms meant that an infectious individual could infect others for about three weeks before realising that he was ill .

Infection was by droplet : like flu . It was like Ebola on steroids .

The only thing that helped a bit then was quarantine . This helped in the later recurrences of the Plague . A quarantine of 40 days evolved ( still in force in Maritime Law ) .

The Black Death was when the virus hit a virgin population . Plague recurred from 1347 until about 1668 . (300 years : then it vanished mysteriously)

Some people were immune : the CCR5 receptor site of the white blood cells was the seeming entry site for the plague . A mutation called CCR5-delta32 prevented this receptor being used . All known descendants of survivors have this mutation . The present prevalance of this mutation in Europe is about 10 - 15 % , but 0% in other ethnic populations .

The interesting thing is that this same receptor site is the penetration site for smallpox and HIV .

Smallpox appeared in the 1500's and the last occurence of the Plague was in 1668 (the Great London Plague) . This mysterious disappearance of the Plague gives rise to the suspicion that they are related : a less deadly disease like smallpox will outcompete the Plague for access to the CCR5 receptor site in non-immune survivors . Since the Plague as Pandemic was a statistical phenomenon , the Plague was replaced by Smallpox.

Ironical effect : the smallpox innoculations in Africa would have made the populations exposed to SIV and HIV more open to infection .

At present there is some accusations that the Smallpox vaccinations in Africa were contaminated . The truth seems scarier : The very process of innoculation opened up the avenue to HIV . The innoculation campaigns created virgin populations .

A further complication is that everybody without the delta32 mutation is now again open to the Plague and every other bug that uses CCR5 in Africa Europe and America .

An interesting speculation : will infecting a HIV positive person with smallpox have a beneficial effect ? Maybe a weakened form that only ties up the CCR5 receptor site?

What if the Plague reappears ?

Will we have to fight plague with plague ?


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