Pandemics and pathology: a reflection on influenza, HIV/AIDS and SARS (COVID-19) pandemic infections.

The COVID-19 pandemic has reminded pathologists of our significant roles in the management and understanding of rapidly spreading and dangerous pathogens, from identifying the agent to characterizing the clinical pathology to managing the dead. Cellular pathology - through autopsy - has depicted the main features: viral pneumonitis, acute lung injury, organising pneumonia, secondary bacterial pneumonia, thrombophilia and infarction, and systemic inflammatory response syndrome with multi-organ failure. These are similar to another viral pandemic of the 20th century, H1N1 influenza; but contrast with the second major more complicated pandemic, that of HIV/AIDS. The outcomes of these infections are compared, along with seasonal influenza and SARS-1-CoV disease. Work to be done on COVID-19 includes characterisation of the emerging 'long COVID' syndrome, and monitoring the complications of therapies and vaccination programs.