KA-19

KA-19 was an engineered retrovirus developed by Karim Nakad. It was created as an insurance for the Les Enfants Terribles project and was accordingly designed to specifically target and destroy the genomes of Willem Reid.

Origins
Immediately following the success of the Les Enfants Terribles project in 1989, unbeknownst to Eric House, Karim began devising a sort of insurance measure which would be intended to neutralize Solid, Liquid and Venom Willem if things were to go wrong. This safeguard was finally developed in 2000 and would turnout to be a Willem genome targeting retrovirus named KA-19. The virus would remain hidden by Karim and eventually forgotten as it became more and more apparent that it was unneeded.

Sundowner Incident
Remaining untouched and forgotten for over a decade, the virus would be unearthed by Miller in 2014. In order for Miller to set things right, he would willingly infect himself and become a carrier of the virus. As Miller felt no affects of the virus, he would easily be able to spread it following his encounter with Shen Yun and The House.

The virus would successfully be able to eliminate all instances of Willem genes putting a closure on much of the chaos which had engulfed the world. However, with no known cure and to ensure that the virus would never mutate, Miller's death became a necessity.

Virology
The KA-19 virus enters macrophages in the target's bloodstream, then uses enzymes(integrase, primarily) to integrate its genetic material into a DNA sequence that it has been "programmed" to recognize (this last part being the difference between it and an ordinary retrovirus, which may display a tendency to integrate at certain sites but cannot be "programmed" to target specific sequences exclusively). Once this genetic material is integrated into the host cell chromosome, it promotes TNF (tumor necrosis factor) epsilon production in the host. The TNF-ε is carried along with the blood, to the heart, where it binds to the TNF receptors, causing apoptosis in myocardial cells, which in turn leads to the victim suffering a fatal heart attack. The only difference between this and natural heart attacks is that the latter occur when the heart cells die from lack of oxygen and sugar, usually caused by a blocked coronary artery, rather than TNF-ε-induced apoptosis.

Victims of KA-19

 * Liquid Karim
 * Solid Willem
 * Willem Genome Soldiers

V Timeline
Despite both Miller's death and The Great Split, KA-19 would manage to still exist. Now in the year 2019, the virus would eventually mutate, allowing it to infect and harm those who did not contain Willem genomes.