Investigators in protective gear remove a van from an address in Winterslow, England on March 12, authorities continue to investigate the nerve agent attack on a former Russian spy.
Credit: Matt Cardy/Getty

A Soviet-era poison called Novichok was used to poison an ex-Russian spy and his daughter last week in England, U.K.

Prime Minister Theresa May told Parliament today (March 12).

This announcement shows that U.K. authorities were right to suspect that a type of nerve agent had poisoned the former spy, Sergei Skripal, 66, and his daughter, Yulia, 33, who were found stiff and unconscious on a park bench in Salisbury, England on March 4. Both Sergei Skripal and Yulia Skripal are critically ill and in intensive care.

But  what is Novichok and how does it affect humans? [5 Lethal Chemical Warfare Agents]

Novichok, which means "newcomer" in Russian, is a Soviet-era class of nerve agents that was created in the 1970s and 1980s as an attempt to get around the Chemical Weapons Treaty, according to "Responding to Terrorism: A Medical Handbook," published in 2010. That's because the treaty banned chemical weapons that have a certain chemical structure, and Novichok has a different structure.

Despite this structural difference, Novichok agents act like other nerve agents by binding to and inactivating cholinesterase, an enzyme that the nervous system uses to communicate with muscles.  

"The reason you die from these [nerve agents] is very simple," said Dr. Lewis Nelson, chairman of emergency medicine at Rutgers New Jersey Medical School, who is not involved with the Skripals' treatment. "If your muscles don't work you can't breathe, and if you can't breathe you eventually die."

Like other nerve agents, Novichok causes a range of symptoms. Victims can develop pinpoint-size pupils, digestive problems and excess salivation and tears, Nelson said. Typically, muscle spasms and seizures occur and the heart stops beating.

Novichok agents can take the form of an ultra-fine powder, according to the handbook. The poison is made when two separate, nontoxic components are mixed into an active nerve agent.

If Novichok agents are inhaled, symptoms can occur in 30 seconds to 2 minutes, the handbook reported.

In addition, a little bit of Novichok can do a lot of damage; it's five to eight times more potent than VX nerve agent, the handbook reported. This means that it takes less Novichok to cause the same amount of harm that VX does, Nelson said.

Because so little of it is needed, Novichok agents are challenging to detect in victims. But toxicologists could probably find them if they know what they're looking for, Nelson said. "There are ways around it by concentrating the sample," he told Live Science.

If a person is exposed to Novichok agents, they should be immediately connected to life support and decontaminated — that is, their clothes should be removed and their skin washed with soap and water. A number of antidotes, including atropine, pralidoxime and diazepam can be lifesaving, Nelson said.

But even these treatments don't guarantee recovery. "Novichok agents are reported to produce more permanent injury, even following appropriate nerve agent antidote treatment," the handbook said.  

Original article on Live Science.