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Causes of Plague in London, 1664-1665
- It was a recurrence of the Bubonic Plague that occurred in the 1340s, which killed at least a third of the European population. Subsequent outbreaks of it to 1722 are called the Second Plague Pandemic.
- People thought it had been carried to England in bales of cotton imported from the Netherlands. Plague had been intermittent there since 1654.
- Some people believed “miasmas”, foul air and/or dirty environments or crowded living conditions caused it. Rats lived in thatched roofs, for instance.
- Some people believed it was a divine punishment from God for sins committed by individuals and/or societal groups.
- Today we know that fleas carry a microorganism called Yersinia pestis from one rodent/rat/animal to another.
- When the levels of infection reach a certain level in the rodents/rats/animals, the fleas jump to a person and bite him or her, seeking a new host.
- Also involved were a combination of immunity patterns and demographic changes. Humans and rodents build up immunity over time. Many people were migrating to London to live from rural areas where people had less immunity.
- Transmission from person to person happened either through the air (pneumatic), or through the blood (septicemic). While people in the 17th century did not know about germs, some, like Defoe, understood that person to person transmission happened through the air by proximity of persons.
- Asymptomatic or ill people moving around or travelling carry it from one place and person to another.