countermeasure means a drug (as that term is defined by section 201(g)(1) of the Federal Food, Drug, and Cosmetic Act ( 21 U.S.C. 321(g)(1) )), biological product (as that term is defined by section 351(i) of this Act ( 42 U.S.C. 262(i) )), or device (as that term is defined by section 201(h) of the Federal Food, Drug, and Cosmetic Act ( 21 U.S.C. 321(h) )), that the Secretary determines to be a priority consistent with sections 302(2) and 304(a) of the Homeland Security Act of 2002— (i) to diagnose, mitigate, prevent, or treat harm from any biological agent (including organisms that cause an infectious disease), toxin, chemical, radiological, or nuclear agent that may cause a public health emergency affecting national security