Synergism between respiratory viruses and bacteria.

Many studies concerning the etiology of acute and chronic diseases of the respiratory tract have been triggered by outbreaks of epidemic influenza in man. Parsons,' in his report of the influenza pandemic of 1889-90, summarizes the evidence for and against the many hypotheses concerning its etiology which had been considered over the centuries. Shortly before this pandemic, several groups of organisms associated with acute upper and lower respiratory tract infections had been identified. investigators, particularly in Germany, isolated the above organisms from the secretions of the respiratory tract, lungs, or blood of patients having influenza and ascribed a primary etiological role to them.' Pfeiffer isolated the bacillus which bears his name from the secretions and tissues of patients suffering from or dying of influenza.' Following his report, the frequent close association of Pfeiffer's bacillus with human influenza infections was widely confirmed by others, and this organism came to be considered generally as the specific cause of epidemic influenza."' With the worldwide outbreak of influenza in 1918, an opportunity presented itself to investigate with improved methods and design the etiological role of Pfeiffer's bacillus in this disease. Its primary causative role was soon questioned, for outbreaks of influenza during the summer months of 1918 occurred, from which cases the influenza bacillus could not be isolated. Jordan,' the British Ministry of Health,7 and David and Robert Thomson,8.9 reviewed the bacteriological findings from thousands of published reports made during the 1890 and 1918 pandemics and other lesser influenza outbreaks. In summarizing the available evidence, bacterial organisms in epidemic influenza were relegated to the etiological role of secondary invaders acting alone or in symbiotic fashion to produce the often severe complications. A few years before the 1918 pandemic of influenza several studies were reported which suggested that epidemic influenza and the common cold may be due to viruses. During this outbreak many studies were carried out * Hastings Professor of Medicine and Pathology.