How to Diagnose a Medieval Disease

Modern Plague

The Third Plague Pandemic

• Previous Pandemics– First Pandemic: The Plague of Justinian (6th – 8th c.)– Second Pandemic: The Black Death (1346-1353)– Third Pandemic: 1855-1959 (esp. China and India)

• Research in Hong Kong, 1894– Pre-antibiotics (discovered in 1929)– Alexandre Yersin– Bacillus Pasteurella pestis (renamed Yerinia pestis

and commonly called Y. pestis)

Yersinia pestis

• Bubonic Plague– Lympathic System– Animal to Human

• Septicemic Plague– Blood Steam– Flea happens to inject bacteria directly into blood steam

or Plague infection spreads to blood• Pneumonic Plague– Respiratory System– Primary Infection – Inhale Bacteria (Human to Human)– Secondary Infection – Plague infection spreads to lungs

Common Symptoms• Common Symptoms

– Fever, weakness, fatigue, headache• Bubonic Plague

– Incubation Period: 7-20 days– Chills, buboes (esp. groin, armpit, neck), muscle aches, petechiae

(subcutaneous bleeding)• Septicemic Plague

– Incubation Period: 1-6 days; 100% fatal without treatment– Chills, abdominal pain, subcutaneous bleeding, diarrhea, vomiting, bleeding

from mouth/nose/rectum, petechiae (subcutaneous bleeding, gangrene, shock• Pneumonic Plague

– Incubation Period: 1-3 days– Coughing, coughing up bloody or watery mucus, nausea, dizziness, vomiting,

shortness of breath, chest pain, pneumonia, respiratory failure, shock.– Symptoms can appear very similar to influenza (שפעת), anthrax (גחלת), Q

fever (Q קדחת), tularemia ( טולרמיה \ הארנבות (קדחת

From: http://gentlemint.com/tack/153967/

Bubonic Plague: Buboes(Swelling of Lymph Nodes)

Plague: Petechiae(Spots Caused by Broken Blood Vessels)

Septicemic Plague

Gangrene

Agent of Spread

Tropical Rat FleaXenopsylla cheopis

הדבר פרעוש

Identifying Medieval Plague: Problems

Graham Twigg (1984)

• Entomologist• Read English accounts• Seasonality

Death Rates

• The Problem– Modern Plague has a death rate of roughly 14%

• Possible Explanations (Not Plague)– Anthrax (Twigg)– Hemorrhagic fever (similar to Ebola) (Scott & Duncan)– Don’t know, but not plague (Cohn)

• Possible Explanations (Plague)– A combination of plague and typhus (טיפוס)

(Shrewsbury)– Many secondary deaths

Seasonality

• The Problem– Bubonic Plague should be active mainly in Summer and

Fall. Pneumonic plague mainly in winter when people are cooped up.

– The medieval plague peaks in Fall and doesn’t seem to have a rest period.

– The tropical rat flea cannot survive Fall temperatures, especially in northern regions like England

• Possible Explanations– A different disease?– A different type of flea? (see next slide)

Rats

• The Problem– Where are all the rats? Not mentioned in medieval

sources– The medieval “black rat” (Rattus rattus, מצויה (חולדה

tends to avoid humans– The rats would have to die before rat fleas would jump

to humans• Possible Explanations– More than 30 species of flea can carry the plague,

including the human flea, pulex irritans ( האדם (פרעוש

Symptoms

• The Problem– Many sources don’t mention buboes at all; others place

them all over the body (instead of just at the groin, armpit, and neck)

– In general, the descriptions of symptoms are too vague for a definitive identification

“In a sense, Preclinical disease was socially constructed. People reduced all illnesses with common symptoms into a single diagnosis.”

--Theilmann and Cate

Spread

• The Problem– A study on 19th century China shows spread of

only a few miles per year

The Question of Immunity

• The Problem– Humans do not develop immunity to Y. pestis.– The Plague kept returning, but it never did as

much damage as the first time, suggesting acquired immunity.

• Possible Explanations– There is debate over the premise that humans

cannot develop immunity to Y. pestis.

DNA Evidence

Polymerase Chain Reaction (PCR)• 1998 Study (Marseille Team)

– Plague Cemeteries from 1590 and 1722– Teeth– Y. pestis found in 50% of plague teeth and none of control sample

• 2000 Study (Marseille Team) – Begins using PCR testing– Found Y. pestis in a 14th century site

• Sharp Criticism of the Methods and Results of the 1998 and 2000 Study

• 2003 Study (Munich Team)– Replicated the earlier methodology and found Y. pestis in a sixth-century

site as well (part of First Pandemic, 6th-8th century)• 2004 and 2007 Studies (Marseille Team)

– Confirmed Y. pestis in sixth-century sites

F1 Antigen Test

• 2004 Study (Tübingen Team)– Skeletons from a mortuary chapel (17th c.)• 12 Bodies covered with lime (סיד) (presumably plague

victims)– 10 out of 12 tested positive for Y. pestis antigens

• 12 Bodies not covered with lime• Also used PCR

• 2009 Study (Turin Team)– Confirmed Y. pestis antigens in sixteenth and

seventeenth century sites

Criticism of DNA Evidence

What is the value of the DNA Evidence if they don’t explain anything about the differences between modern and medieval plague? (Cohn)

Recent Studies

• 2010 (Mainz Team)– 5 Sites all around Europe (England, France, Germany,

Netherlands, Italy), 14th-17th centuries– F1 Antigen analysis showed Y. pestis in all sites– PCR analysis showed Y. pestis in three sites– Found two different strains of Y. pestis

• 2010 (International Team)– Attempt to sequence the history of Y. pestis– Concluded that it originated in China

• 2011 (Marseille Team)– Used both methods and found Y. pestis in Venice

Hypotheses: Biological Factors

• Genetic alteration in fleas may have made it easier to transfer to humans

• Iron deficiency in humans increases susceptibility to the plague

• Other infections, such as salmonella and other Yersinia bacteria prevent infection of Y. pestis.

• There are at least 4 major strains of Y. pestis. The one studied in modern outbreaks (Y. pestis orientalis) is not the same as the Black Death strain (Y. pestis medievalis).– How many active during the Black Death?