The disease leading to the pandemic around year 0 was called "the Rash illness", or "the Rash" for short. In the year 90, people refer to "the Great Illness" or "the Illness" when talking about the primary infection they fear. It is not yet clear whether these actually are, or at some point were, the same disease.
Sources of Information Edit
The prologue presents bits and pieces of information as published by the governments, and ensuing discussions on mass media like TV. There is a strong undertone suggesting that the administrations' communiques are far from complete, though, or possibly even downright disinformation to uphold the public order.
A considerably more trustworthy source of information appears when the expedition team, while raiding spot 24, find sort of a logbook of one of the medics running it in year 0.
Source and Properties of the Disease Edit
As far as Europe and the Nordics are concerned, the Rash first appeared on the radar two days prior to what is now called "year 0, day 0", in the shape of a boat with eleven illegal refugees arriving in Spain.
The first understanding of the course of the disease (as discussed in Dalsnes) summarized it as "bedridden for a week", plus unnamed "serious" complications possible for very young, old, or pregnant patients. The outlook of one, or maybe several, weeks of the national workforce being bedridden prompted some governments to think about quarantining their nations already.
On day 3, in the TV segment shown on the ferry to Bornholm, its incubation period is said to range between several days and "almost two weeks", with the patients already becoming infectious - to humans and other mammals - before being symptomatic. Advice given to avoid infection seems to be in agreement with a droplet infection vector, but recovery of the original patients is still (erroneously) expected to begin shortly. The first symptom are the namesake rashes, "commonly followed by vomiting and sporadic fever spells".
On day 5, news broke that two of the original patients - "entering their fourth week of infection" - had died and the other nine were comatose and unresponsive to attempted treatments, contradicting earlier claims of their being "in decent condition". By day 9, only four were still alive.
The case of , and additional information given by the author on that page, suggests that the "fourth week" statement was somewhat mistaken, though. The first photo of her, labeled as taken on 15 October, supposedly shows the typical development "a week, possibly two in some cases," after the appearance of the first spots - which, in turn, happens within two weeks of the infection, leading to the universal duration of quarantine. However, the last photo of Hilde showed her - apparently dead - on 30 October, placing her death 5+ weeks after infection.
No mention of the Rash causing disfigurement, fusion of bodies, control or modification of mental states, or any kind of patients bouncing back from death was made before the story arc jumped to year 90. However, it could be that the the icelandic Coast Guard ship Thor was wary of after the third month had been "mutated" already, but the actual cause remains uncertain.