A programming oversight enabled the debuff to disperse beyond the site of the Hakkar boss struggle and to wow classic gold the world at large. Hunter characters may summon and discount pets to fight in their side at will. Once ignored, all of the effects on the pets have been paused until it's known as back out again. In consequence, the pets would contract Corrupted Blood through the boss fight, disappear and then display the symptoms again elsewhere in the world map when they were again summoned. There it would spread to other pets and players which came in contact with them.
Cities such as the dwarven city Ironforge and orc town Orgrimmar were overrun in hours. Non-playable personalities, who could not die due to special coding, could also catch the impact, meaning any player who passed by them could get Corrupted Blood.
Once word got out, players searched frantically for news about what was going on.
"The entire world chat would explode any time a city dropped," says Nadia Heller, an ex-World of Warcraft player whose persona lived through the episode. "We kept a close eye not just on our guild conversation but on world chat as well to determine where not to go. We didn't want to grab it."
The spread of Corrupted Blood, and the participant's behavioral changes to it, captured the attention of epidemiologist Dr. Nina Fefferman, that was a buy classic gold wow player at the time of this incident. In 2007, both published a paper that detailed their findings, including complicated models of individual behaviour during a pandemic. Fefferman says the episode has helped inform her current research into predictive modeling around covid-19.