ACE2 and viral infectious disease: By improving molecular imaging of cellular targets of viral infection (such as Angiotensin-converting enzyme 2 (ACE2) receptors in coronavirus 2019 (COVID-19) or cluster of differentiation 4 (CD4) cells in human immunodeficiency virus (HIV) patients) [25], total-body PET imaging may play a vital role in detecting organ involvement and elucidating disease pathogenesis.