Scourge of Odin

Astrid sick from the Scourge of Odin

“	The Scourge of Odin. Just the plague that tore through the archipelago centuries ago, wiping out entire viking villages! [src]	”
	— Snotlout about the disease

The Scourge of Odin is a lethal infectious disease transmitted by blood and said to have disappeared for centuries in the archipelago.

Symptoms

The effects are coughing, pale skin and fatigue. The infected turn pale and start coughing within a day or so. They turn too weak to walk and have a tendency to faint. During the following day, their skin turns pale and eventually into a sickly shade of green and their eyes become bloodshot. Death is said to occur during the third moon.

Cure

The only known cure for this lethal disease is the green saliva secreted by Buffalords. This cure is hard to come by as Buffalords are critically endangered, thought to be extinct and its saliva appears to be volatile and evaporates quickly. The effect, fortunately, takes place almost instantly.

In Race to the Edge

According to Snotlout, the Scourge decimated entire villages. Astrid comes down with the Scourge of Odin when she enters a ship with the infected crew, and the one remaining live occupant reached up to her for help; scratching her arm. As the Scourge of Odin can only be transmitted via blood, she became infected through the scratch. She was eventually cured with Buffalord saliva mixed with the herbs the dragon eats, and the fishing crew were given a proper Viking funeral--their ship set ablaze in honor by the gang. ("Buffalord Soldier")

In Rise of Berk

When the riders found Chicken and Cockatrice, Snotlout think that the latter is infected with the Scourge of Odin, hinting that animals can also contact the disease.

“	Can we please discuss the creepy-Scourge-of-Odin looking chicken that seems to be following YOURS around?	”
	— Snotlout

Victims 

• Astrid Hofferson (cured)
• Viggo Grimborn's Fishing crew
• Villages of the Archipelago (hundreds of years ago)