Not everything we do regarding public health in our country has an impact on other countries. However, the things that do have such an impact are no doubt properly a part of "global health". The things that don't would be purely local public health. But since we don't know at the time that a particular sneeze in Wuhan can have a serious impact in Ouagadougou or London, there is probably a good operational argument for not making a distinction between "public health" and "global health" at all.
HIFA profile: Chris Zielinski: As a Visiting Fellow in the Centre for Global Health, Chris leads the Partnerships in Health Information (Phi) programme at the University of Winchester. Formerly an NGO, Phi supports knowledge development and brokers healthcare information exchanges of all kinds. Chris has held senior positions in publishing and knowledge management with WHO in Brazzaville, Geneva, Cairo and New Delhi, with FAO in Rome, ILO in Geneva, and UNIDO in Vienna. Chris also spent three years in London as Chief Executive of the Authors Licensing and Collecting Society. He was the founder of the ExtraMED project (Third World biomedical journals on CD-ROM), and managed the Gates Foundation-supported Health Information Resource Centres project. He served on WHO’s Ethical Review Committee, and was an originator of the African Health Observatory. Chris has been a director of the World Association of Medical Editors, UK Copyright Licensing Agency, Educational Recording Agency, and International Association of Audiovisual Writers and Directors. He has served on the boards of several NGOs and ethics groupings (information and computer ethics and bioethics). UK-based, he is also building houses in Zambia. chris AT chriszielinski.com
His publications are at www.ResearchGate.net and https://winchester.academia.edu/ChrisZielinski/ and his blogs are http://ziggytheblue.wordrpress.com and https://www.tumblr.com/blog/ziggytheblue