In the first episode of BBC historical drama Wolf Hall, based on Hilary Mantel’s novel of the same name, Thomas Cromwell returns home to find his wife and two daughters have all died during the night, victims of a pestilence – the “sweating sickness” – that is scything through the Tudor world.

The speed of onset of this disease, which saw victims literally being well today and dead tomorrow, and its relentlessly high mortality rate gave the sweating sickness the same aura of terror that we attach to Ebola today.

Sudor Anglicus

Contemporary accounts describe an illness that began with a general feeling that something was not right, a strange premonition of oncoming horror, followed by the onset of violent headache, flu-like shivers and aching limbs.

This was succeeded by a raging fever complicated by pulse irregularities and cardiac palpitations. Death often simply seemed to occur due to dehydration and exhaustion. As one commentator said:

A newe Kynde of sickness came through the whole region, which was so sore, so peynfull, and sharp, that the lyke was never harde of to any mannes rememberance before that tyme.

The sweating sickness first appeared around the time Thomas Cromwell, later chief minister to Henry VIII, was born, at the end of the dynastic Wars of the Roses, and there has been some debate concerning the possibility that it arrived with the invading army of the first Tudor king, Henry VII, in 1485.

By the time it disappeared in 1551 it had caused five devastating outbreaks. To observers on the other side of the Channel, whose countries had apparently remained miraculously untouched (though a later outbreak did spread to Calais), this disease was Sudor Anglicus, or the “English Sweat”.

Doctor without borders

During the Tudor and early Elizabethan eras, the merest rumour of sweating sickness in a certain locality was enough to cause an exodus of those who could afford to leave.

Thomas Le Forestier, a French doctor originally based in England, wrote about the 1485 sickness after his return to France, providing information about its appearance and impact during this first outbreak.

But one man’s name became synonymous with the sickness. Norwich-born and Cambridge-educated John Kays had spent his early medical career travelling extensively on the continent, returning around the end of the reign of Henry VIII with a fashionably Latinised moniker, Dr Johannus Caius. The sweating sickness panic during the outbreak of 1551 gave him the ideal opportunity to make this new name known to everybody.

The fact that the wealthy seemed to be more frequently affected also gave him the opportunity to make money. Despite most of Caius’s patients still ending up dead, he was eventually rich enough to make a splendid endowment to his old Cambridge college, which changed its name to Caius College in his honour. To the rest of us, Caius left his classic description of the disease: Account of the Sweating Sickness in England, first published in 1556.

Medical speculation

A minor academic industry has developed speculating on what sweating sickness could have been.

Given that it had few symptoms other than a violent fatal fever, medical historians have had little to go on. But suggestions that have been made over the years include influenza, scarlet fever, anthrax, typhus or some SARS-like pulmonary enterovirus. All, however, have had some clinical or epidemiological aspect that meant they didn’t quite fit the description on the “most wanted” poster for sweating sickness.

Then in 1993, an outbreak of a remarkably similar syndrome occurred among the Navajo people in the region of Gallup, New Mexico. This episode, known as the Four Corners outbreak after the region of south-western USA in which it was located, turned the attention of sweating sickness investigators towards its causative agent: Sin Nombre virus. Sin Nombre is a hantavirus, a member of a group of viruses that were mostly previously known in Europe for causing a kidney failure syndrome, and a cousin of several tropical fever viruses transmitted by biting insects. The new disease was given the name hantavirus pulmonary syndrome (HPS).

Made in Chelsea

Aside from the similar clinical descriptions of sweating sickness and HPS, one other factor stands out in favour of their equivalence: rich people in Tudor times were more likely to be victims.

The end of the Wars of the Roses meant that people at last felt safe to invest in property without the risk of it being immediately ransacked, and the dissolution of the monasteries created a new upwardly mobile class that suddenly had the means to build. And build they did – Tudor London and the regional cities of England experienced a massive housing boom. Large households needed large staff, and large numbers of people need large kitchens full of large deposits of grain and other foodstuffs. Shortly after the people moved in, the rats and mice followed.

The Four Corners outbreak was due to the presence of Sin Nombre virus within the droppings of deer mice living in the vicinity of the Navajo dwellings. Aerosolisation of the virus when the droppings were disturbed, for instance when a broom passed over them to sweep them away, created an environmental airborne infection.

Whereas nowadays rodents plague the poor, in post-medieval London they were a feature of all levels of society. Rather than try to remove the rats, an almost impossible task, Tudor housekeepers, fastidiously brushing their droppings away, may have released a cloud of hantavirus-loaded dust, triggering the sweating sickness across England. All this assumes, of course, that the sweating sickness was an early variant of HPS. Other candidate pathogens have generated other explanations and scenarios.

So where did it go?

Sweating sickness had disappeared by late Elizabethan times. Its reign of terror barely lasted a century. If indeed it was an ancient variant of HPS, we can perhaps speculate about what led to its demise. The virus may have mutated to a less virulent form, perhaps in the process acquiring the capacity to be passed between humans as a more benign feverish illness, rather than being just a sporadic environmental hazard. Or perhaps its evolutionary trajectory took it in the other direction, becoming more fatal to its rodent hosts, thereby reducing the quantity of infected droppings around human habitations.

There is a third possibility – we know that the climate of Europe was becoming progressively colder from the late middle ages onwards. Perhaps some subtle change in rodent ecology made life harder for the virus. For instance the Four Corners HPS outbreak was linked to the El Niño climatic oscillation. We’ll never know for sure. Much of the mystery of sweating sickness remains. However, we do know that hantaviruses are still with us, and their day could come again.