Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
Virus pneumonia of pigs (VPP) is an inflammation of the lungs usually confined to the anterior-ventral portion and lower borders of the apical and cardiac lobes. It is usually a chronic disease that may develop into acute and subacute forms, particularly if "secondary break down" occurs due to secondary bacterial invasion. The disease is characterized by a chronic cough, consolidation of the anterior ventral portions of the lung, and secondary bacterial invasion. It is a distinct disease and is in no way related to the common swine influenza described by Shope in 1931.
"Virus Pneumonia of Pigs,"
Iowa State University Veterinarian: Vol. 22
, Article 4.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol22/iss2/4