APA guidelines suggest you write out the full name of an organization each time you reference it in the text, whether in a signal phrase or an in-text citation, since the reference must be clear. However, when you reference a group such as the CDC, which should be well-known to your readers, you may use the acronym for references after the first one. You should use the CDC acronym just like this, with no periods between the letters.
To reference material published by the CDC without any other author credited, you should use the CDC designation as the author on the References page as well as in the in-text citations. Spell out the name in full, Centers for Disease Control and Prevention, on the References page, whether you include it as an organizational author, publisher or Web site. If the CDC authored the work, the entry should be alphabetized according to the word "Center," the first word in the entry. Note that the official designation does not begin with "the."