The Times
March 11, 2005

How horrors of the plague made Europe safer from Aids scourge
By Russell Jenkins

LIFE was nasty, brutish and short when the waves of plague swept through
Europe right up to the 18th century.

Scientific research now suggests, however, that the terrible suffering of
our forebears means that a significant proportion of modern Europeans is
resistant to Aids.

Research by two British biologists published in the Journal of Medical
Genetics suggests that around 10 per cent of Europeans enjoy such protection
as a direct result of the series of plagues that swept across the Continent
from the Middle Ages onwards.

Biologists have known for some time that people carrying a particular
genetic mutation, known as CCR5-delta32, remain free of the disease. The
mutation prevents the HIV virus from entering the cells of the immune
system.

It is also a continuing puzzle as to why the strains of HIV that have swept
through Africa have made much less of an impression in Europe.

The new theory suggests that the CCR5 mutation was a by-product of the
European plagues. The proportion of people carrying the natural resistance
rises dramatically in Europe and particularly Scandinavia, where the figure
is 14-15 per cent. It is relatively low in countries bordering the
Mediterranean and not found at all in sub-Saharan Africa, Asia or among
native Americans.

Christopher Duncan and Susan Scott, based at the University of Liverpool's
School of Biological Sciences, suggest that the natural protection from HIV
can be attributed to the peculiar history of the plague from classical
antiquity to 18th-century Denmark.

They have put forward a mathematical matrix showing how the frequency of
genetic mutation rises with each stage of plague outbreak from the Black
Death in 1347 to the Great Plague of London (1665-66) and beyond to the
Plague of Copenhagen more than half a century later.

Using a computer model, they demonstrate how the pressure of natural
selection increases the number of those carrying the resistance from around
one in 20,000 at the time when plague devastated Europe, particularly
France, during the mid-14th century to one in ten three centuries later.

Professor Duncan and Dr Scott, authors of The Return of the Black Death,
published last year, are adamant that these plagues were not bubonic but
epidemics of viral haemorrhagic fever that used the CCR5 receptor as the
"entry port" into the immune system. These lethal haemorrhagic fevers ‹
whose modern version is Ebola fever ‹ are believed to have occurred as far
back as antiquity. They were recorded in the Nile Valley from 1500 BC and in
Mesopotamia (700-450BC), Athens (430BC), the plague of Justinian (AD
541-700) and the plagues of the early Islamic empire (AD 627-744).

If the plague struck a village carrying off half the population, those with
the natural resistance became a higher proportion of the survivors. Then
they handed it on to their descendants, who were also more likely to survive
a plague.

Professor Duncan dismisses other theories which claim that resistance to
Aids can be attributed to smallpox or bubonic plague. He is less sure that
his work will have any practical impact on medical research and is not
hopeful that the genetic mutation, can be reproduced artificially to create
protection.

GENETIC RISK OF DISEASE

Particular genetic traits, arising either by natural selection or by
accident, are known to influence risk of getting diseases

- Malaria: in areas where malaria is endemic, more people are born with
genes that confer protection

- vCJD: all cases of the human version of ³mad cow² disease occurred in
people with a particular genetic make-up, shared by about 40 per cent of
population

- Alzheimer's and Parkinson's disease: inheriting a version of a gene APO-E
can increase the risk of Alzheimer's

http://www.timesonline.co.uk/article/0,,2-1520635,00.html