 pathogenesi viral influenz pneumonia mice pathogenesi influenz pneumonia mice studi electron microscopi mice inocul 1 5 ld pr8 influenza viru kill vari interv inocul observ light microscopi correl electron microscopi order evalu lesion produc peripheri earliest lesion focal area edema alveolar line cell capillari endothelium interpos basement membran caus appreci thicken blood-air pathwai hypertrophi degener desquam alveolar line prolifer alveolar macrophag complet consolid progress 1 week infect central area lung differ 3 dai infect noncili bronchiolar cell consider hyperplasia endoplasm reticulum apic cytoplasm edema viral particl matur lumen surfac cell releas bronchiolar lumen bronchiolar cell ciliat noncili underw degener slough bronchiolar lumen regener epithelium stratifi surfac cell elong flatten peribronchiolar interstiti tissu gradual total infiltr cell mononuclear type 