The "21 viral types that wreak havoc with the human body represent an insignificant fraction of the 100 million viral types on earth. Most viruses are actually vital to our very existence." So says Peter Pollard, Associate Professor, Griffith University, Queensland, Australia here:
theconversation.com/viruses...
So viruses, like bacteria, get bad press based on the very small number that can make us ill.
By studying how viruses work, we can engineer them to assist in the study of genetics and even in the development of new cancer therapies. CAR-T therapy, which is showing great promise in the treatment of a range of cancers including CLL, relies on genetically engineering human T cells with a disabled HIV-derived lentivirus that retains one essential feature of HIV - the ability to insert new genes into cells.
Neil
Photo: Flowering Myrtle Leaf Milkwort or Bellarine Pea (Polygala myrtifolia L.), with thanks to Jay as usual for the identification.
Why we need to track the absolute lymphocyte count (ALC), not white blood cell count (WBC) to monitor CLL
Research shows blood cancer patients generate strong T cell immunity after SARS-CoV-2 vaccination
CLL and vaccination 
On the possible use of mushrooms and natural supplements, and their potential benefits, with citations
