The U.S. Department of Health and Human Services (HHS) has published a series of resources discussing the characteristics and challenges of “fourth generation agents” and providing guidance to segments of the emergency response community. Also known as “Novichoks” or “A-series nerve agents,” fourth generation agents are chemical warfare agents that pose several unique challenges in terms of toxicity, detection, persistence, and potential for delayed onset of symptoms. A fourth generation agent was used in an incident in the U.K. in 2018, prompting the U.S. National Security Council to convene a federal interagency working group to identify and develop resources to help the emergency response community prepare for and respond to a fourth generation agent incident if one ever occurs in the U.S., as well as support the development of specific guidance and training to enhance overall preparedness efforts. HHS intends for the resources it published to meet the needs of U.S. emergency response professionals who sought to learn more about these agents and how to protect themselves and respond if such incidents ever occur in their communities. Read the awareness guides at HHS.