In the event of a biological weapon attack on the U.S., it will be up to the U.S. Postal Service to deliver needed medications to Americans, under an executive order signed Dec. 30 by President Barack Obama.

The leaders of the Health and Human Services and Homeland Security departments have six months to create a plan for the Postal Service to distribute medicines, with "anthrax as the primary threat consideration." In such events, letter carriers delivering medications may be accompanied by local law enforcement officers.

The plan must include provisions for getting medications to federal employees with essential responsibilities during an attack.

Anthrax garnered attention as a biological weapon in 2001 after letters containing anthrax powder were mailed to news organizations and two Democratic senators. Five people died, including two postal workers in Washington, and 17 were infected, including several Postal Service employees.