Black Lung

Caused by bacteria that reproduce in the lungs, Black Lung is an infectious disease that has an 8% fatality rate when untreated. The bacteria were discovered during YY 1 on a scientific Exploration, and scientific experiments at the Medical Laboratory gave a good indication of exactly how dangerous the disease could be for humans. Security protocols were developed to help stave off infection.
Obedience of the security protocols reduced over the years, and during YY 5 the first outbreak happened. While most of the population properly obeyed the increased security protocols and isolated when possibly infected, some refused to listen and didn't take health complaints serious. The resulting death toll proved that the theoretical 8% fatality rate was estimated correctly. For the rest of the population, developed treatments kept casualties to a minimum.
Emergency laws mandated serious counter-measures, while the Science Department worked hard on vaccines. After trials with Homesteaders proved successful, everyone was provided with bi-annual vaccine injections. However, the vaccines did not offer full immunity. In response, the military government made the default protection measures a part of Martial Law, allowing them full control over the Mask Mandate and mandatory health checks.
Because humanity has been spreading over Ymir, it has been deemed impossible to prevent all infections. Instead, strict protocols are designed to help detect and prevent infections, to essentially buy the population time and prevent outbreaks from occurring. Thanks to the protocols, only 31 small and 7 large outbreaks have occurred.

Fatality rate (untreated)

8%

Fatality rate (treated)

0.1%

Remnant damage (untreated)

19%

Remnant damage (treated)

3.1%

Yearly casualties

18

Vaccine effectiveness

81%~93% prevention of infectiousness

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Symptoms

Black Lung bacteria infect the lungs. In the first stage, this causes a growing ticklish feeling, while the bacteria spread to cover the entire lung. In the second stage, black mucus is coughed up and fevers develop. In the third stage, high fever develops, while the infected starts growing delirious. This may result in a lack of self-control that manifests itself in fits of rage. Eventually, sheer exhaustion may lead to death.

Wildlife impact

Most animals on Ymir are resistant or immune to Black Lung. However, weaker specimen of Taurus species will fail to resist it, and in their delirious state attack predators. Ursa Majors that consume said animals will get infected, turn aggressive, and start seeking out other animals to kill. Eventually, an infected sleuth of Ursa Majors will start roaming, seeking out open space and stampeding until death.