Organism of the week #24 – Danse Macabre

For three centuries, the Black Death was routinely epidemic in London. The first outbreak – in 1348 – probably killed half the population of England; the last outbreak – from 1665 to 1666 – probably killed a quarter of the population of London.

In 1665, Isleworth was a small village several hours’ walk (or row) from London proper, but the Great Plague found its way there anyway. As in many places, so many died that digging individual graves became impractical, so instead, the bodies were interred in communal plague pits.

Isleworth is one of the few places in present-day London where there is evidence above of the burials below. A cairn of stones and a yew tree sit atop the pit and mark the resting place of the 149 people who died there.

Yew trees (Taxus baccata) have long had an association with churchyards. The optimistic may consider this appropriate because yews are an evergreen reminder of the life eternal; the cynical may have other analogies to draw.

Since the 1980s, there has been some debate about the cause of the Black Death. The majority of evidence pointed to the bacterium Yersinia pestis, a parasite of rats and other rodents that gets from place to place in the guts of fleas, and causes swelling of lymph nodes, fever, coughing, bleeding under the skin, gangrene and – all too frequently – death.

In particular, an outbreak of Y. pestis plague that started in China in 1885, and continued worldwide until 1959, had similar symptoms to those reported by mediaeval scholars for the Black Death. However, some remained unconvinced, and pointed the finger instead at haemorrhagic fevers, anthrax, or other agents.

Recent evidence from DNA sequencing of samples taken from plague pits and other burials appear to back up Y. pestis as being the culprit for both the mediaeval Black Death and the even earlier Justinian Plague, which devastated the Byzantine Empire in 541-542.

Plague is currently easily treated with antibiotics like streptomycin if caught early enough, but it’s never really gone away: rodents still carry plague in the US, India, China, Brazil, and southern Africa, and all of these countries have reported infections in the last 40 years.

It’s strange to think that one of the greatest killers in all of human history, exists not just in GCSE history books, but also out there in the real world.

Waiting patiently in the shadows.