The cause is the most mysterious aspect of the disease. Commentators then and now put much blame on the generally poor sanitation, sewage and contaminated water supplies of the time, which may have harboured the source of infection. The first outbreak at the end of the Wars of the Roses means that it may have been brought over from France by the French mercenaries whom Henry VII used to gain the English throne, particularly as they seem to have been immune. However, the Croyland Chronicle mentions that Thomas Stanley, 1st Earl of Derby used the "sweating sickness" as an excuse not to join with Richard III's army prior to the Battle of Bosworth Field.
Relapsing fever has been proposed as a possible cause. This disease, which is spread by ticks and lice, occurs most often during the summer months, as did the original sweating sickness. But, relapsing fever is marked by a prominent black scab at the site of the tick bite and a subsequent skin rash. No contemporaries noted these relatively obvious signs, so the identification is far from certain.
Noting symptom overlap with hantavirus pulmonary syndrome, several scientists proposed an unknown hantavirus as the cause. A critique of this hypothesis included the argument that, whereas sweating sickness was thought to be transmitted from human to human, hantaviruses are not known to spread in this way. However, infection via human to human contact has been proven in hantavirus outbreaks in Argentina.
Read more about this topic: Sweating Sickness
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