Molecular Pathology of Viral Respiratory Diseases

Virology has long been the gold standard by which advances in molecular biology and methodology have been measured.1 As new molecular tools have been developed, new viruses or variants of older, established taxons have been described. Recent advances in genetic sequencing and amplification technologies were pivotal in detecting and describing the two newest agents with a tropism for the respiratory system, severe acute respiratory syndrome (SARS) and avian influenza virus,2–4 both of which have the potential to be pandemic agents with a high mortality and morbidity rate. The rapid development of specific molecular tests led to effective public health measures to be put in place to successfully quarantine these agents thus far. The identification of these two new agents underscores the fact that the major cause of nonbacterial epidemics in history has been viruses with a predilection for the respiratory system. The classic example is the global “Spanish flu” pandemic of 1918, attributed to causing the deaths of 20–40 million people within 1 year, a mortality rate greater than that recorded for World War I and the 4 worst years of the Black Plague (AD 1347–1351) combined.4–7