Professional and government organizations are important resources for public health efforts. Their audience is typically either the general public other professionals in the field. Many of them focus on public health education and outreach, and many also report vital statistics and public opinion information. They are not peer-reviewed in the same way that many research articles in academic journals are, but most of them are still authoritative and contain quality information. Remember to evaluate your sources using lateral reading!
Information found on these sites is typically cited as a web page. Check out the guide on APA for information about citing websites, or ask a librarian!