The CDC has the Crisis & Emergency Risk Communication (CERC) manual[1], as well as a website covering this topic[2].
[1] https://emergency.cdc.gov/cerc/ppt/cerc_2014edition_Copy.pdf https://emergency.cdc.gov/cerc/manual/index.asp
[1] https://emergency.cdc.gov/cerc/ppt/cerc_2014edition_Copy.pdf https://emergency.cdc.gov/cerc/manual/index.asp