What Is It?

Created in the early 1950s, VX -- known by its U.S. Army codename -- is the deadliest nerve agent ever created and is the only significant nerve agent created since World War II. A fraction of a drop of VX, absorbed through the skin, can kill by severely disrupting the nervous system. Although a cocktail of drugs can serve as an antidote, VX acts so quickly that victims would have to be injected with the antidote almost immediately to have a chance at survival.

Synthesizing VX to be used as a weapon is complicated and extremely dangerous. It requires the use of toxic and corrosive chemicals and high temperatures in a sophisticated chemical laboratory. Terrorists lacking access to trained organic chemists might be more likely to steal a munition containing VX from a poorly guarded chemical weapons depot in a country such as Russia.

What Are the Symptoms of Exposure?

Like all nerve agents, VX disrupts the transmission of communications between nerve cells. Symptoms may occur within minutes or hours of exposure, depending on the dose. Death usually occurs within 15 minutes after absorption of a fatal dose.

In mild cases, victims will experience a runny nose, tightness of chest, breathing difficulty, eye pain, dimness of vision and miosis, difficulty in breathing and cough. Moderate cases will cause increased eye symptoms with blurred vision, drooling and excessive sweating, severe nasal congestion, increased tightness of chest and difficulty breathing, nausea, vomiting, diarrhea, cramps, weakness, twitching of large muscle groups, headache, confusion and drowsiness. Severe cases cause involuntary defecation and urination, very copious secretions, twitching, jerking, staggering and convulsions, cessation of breathing, loss of consciousness, coma and death.

How Is It Treated?

Atropine is the antidote of choice for VX exposure through inhalation and ingestion. The primary mode for decontamination through skin contact of chemical agents is soap and water. A 0.5 percent hypochlorite solution can be used. If VX comes into contact with a victim's eyes, they should immediately be flushed with water for 10 to 15 minutes. A victim should then don a respiratory protective mask.

As with other nerve agents, the most effective treatment for VX is the immediate injection of a mix of the drugs atropine and pralidoxime chloride, which counteract the effects of the nerve agent on the peripheral nervous system and help victims breathe; and diazepam, which counteracts the central nervous system effects of VX, including seizures. U.S. military personnel are equipped with auto-injector kits containing the antidotes. But the drugs must be administered immediately upon exposure to VX.

Victims who inhale VX should also be given access to fresh air. Those whose skin has touched VX should be washed with soap and water. Another chemical, pyridostigmine bromide, can be given before exposure to increase resistance to VX.

Who Has It/Where Can It Be Found?

The only countries that have admitted to having VX or a closely-related agent are the United States and Russia. The United States has destroyed about 9 percent of its VX stockpile, and Russia has promised to eliminate its own supply of a VX-like agent. Experts say Iraq successfully weaponized VX sometime in the late 1980s and almost certainly still has VX stockpiles. Syria has reportedly successfully produced VX or a similar agent and tested missile warheads armed with VX.

Some experts and Iraqi defectors say that Saddam Hussein used VX against Iranian forces in both the 1980-1988 Iran-Iraq War and the 1988 chemical attack on Iraqi Kurds in Halabja.