VX is a nerve agent which was developed in the United Kingdom by scientists who were initially trying to design orthophosphates for use as pesticides. Researchers quickly realized that the chemicals they were developing were in fact extremely dangerous and lethal, and they came to be known as V-series nerve agents. Production, stockpiling, and research of V-series agents is prohibited under the Chemical Weapons Convention of 1993, although several nations have chosen to retain parts of their stockpiles for research.
Many people think of VX as a nerve gas, but it is in fact an extremely viscous, pale liquid which looks somewhat like motor oil. The high viscosity of VX makes it extremely persistent, because it is difficult to remove from soil and water, and it can evaporate slowly over time, releasing dangerous VX gas. VX can also be aerosolized, forcing victims to inhale it; aerosolized VX is of great concern, because it could potentially debilitate and kill a very large amount of people as it drifts through the air.
Exposure to VX will ultimately cause death by asphyxiation unless the victim receives medical treatment. Early signs of exposure include twitching, sweating, nausea, shortness of breath, and a runny nose. As the chemical weapon penetrates the body, it interferes with an enzyme in the muscles, causing all the muscles to contract. Ultimately, this will lead to a complete blockage of the airway, causing the victim to die due to lack of air.
The total amount of VX around the world is not known, as most nations are cagey about their chemical weapons programs. This chemical does not appear in nature, so any existing VX would had to have been intentionally synthetically produced, and many nations claim to have destroyed their VX stocks. Despite the fact that the V-series agents were developed in Great Britain, Britain is not known to have any surviving stocks.
Exposure to VX is extremely unlikely, as most nations have agreed that it is too dangerous to be used in the field. Researchers who work with VX do so in very tightly controlled facilities with considerable protections, and they are offered extensive training. In the event that you are exposed to VX, you should remove your clothing as quickly as possible, wash with soap and water, and seek medical attention immediately; in the event of inhalation or ingestion, medical treatment is critical. Medical treatment focuses on flushing the VX from the system and relaxing the muscles of the patient.