Black Death Microbe Same as in Middle Ages But Now Does Much Less Harm

LondonMedievalMap2011-11-07.jpg

Source of map: online version of the NYT article quoted and cited below.

If the Black Death microbe is the same today as in the Middle Ages, maybe the difference in effects is partly due to our better nutrition, health, hygiene, and housing?

(p. D4) The agent of the Black Death is assumed to be Yersinia pestis, the microbe that causes bubonic plague today. But the epidemiology was strikingly different from that of modern outbreaks. Modern plague is carried by fleas and spreads no faster than the rats that carry them can travel. The Black Death seems to have spread directly from one person to another.

Victims sometimes emitted a deathly stench, which is not true of plague victims today. And the Black Death felled at least 30 percent of those it inflicted, whereas a modern plague in India that struck Bombay in 1904, before the advent of antibiotics, killed only 3 percent of its victims.
. . .
If Yersinia pestis was indeed the cause of the Black Death, why were the microbe’s effects so different in medieval times? Its DNA sequence may hold the answer. Dr. Poinar’s team has managed to reconstruct a part of the microbe’s genetic endowment. Yersinia pestis has a single chromosome, containing the bulk of its genes, and three small circles of DNA known as plasmids.
The team has determined the full DNA sequence of the plasmid known as pPCP1 from the East Smithfield cemetery. But, disappointingly, it turns out to be identical to the modern-day plasmid, so it explains none of the differences in the microbe’s effects.

For the full story, see:
NICHOLAS WADE. “Hunting for a Mass Killer in Medieval Graveyards.” The New York Times (Tues., August 30, 2011): D4.
(Note: ellipsis added.)
(Note: the online version of the article is dated August 29, 2011.)

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