Professor Johnson is one of the UK’s leading consultants in respiratory and HIV medicine, practicing at the Royal Free London NHS Foundation Trust (RFL) and the Hospital of St John & St Elizabeth’s. She has been working as a consultant in respiratory medicine and general medicine for over 20 years. She has a special interest in HIV infection, diagnosing, treating clinical complications of HIV and antiretroviral therapy.
In 2005, she was made professor of medicine by University College London. She was the chairman of the British HIV Association from 2004- 2008. She is the elected academic vice president of the Royal College of Physicians.
She has held appointments as clinical director, divisional director and medical director at RFL.
Professor Johnson has a very active research programme and published more than 500 papers on respiratory and HIV topics in peer-reviewed journals.