Bacteriology, Epidemiology, and the Flu
In autumn of 1918, clinicians and researchers at Hopkins became burdened with a war-related epidemic crisis. An unusually lethal strain of what appeared to be either influenza or pneumonia had taken hold in various American training camps. It was also spreading into the civilian population. Several members of the Hopkins staff headed to the laboratories on campus and traveled to training camps in order to investigate the cause of the epidemic. What they hoped to find through the modern tools of bacteriology was the culprit bacterium. What they discovered instead was a complex puzzle and the limits of their tools.
William MacCallum, a Professor of Pathology, is a case in point. MacCallum performed autopsies and lab cultures at Camp Lee and the Johns Hopkins Hospital. Like the vast majority of practitioners at that time, MacCallum suspected that the Pfeiffer Bacillus might be the cause. The pathogen was named after the German scientist Robert Friedrich Pfeiffer, who claimed to have isolated it during a major outbreak in 1892. The more MacCallum probed and cultured, the more he questioned this theory. By the end of the investigation, he had reached the following conclusion, which he communicated to his peers in 1919:
“In Camp Lee we found practically no influenza bacilli…At the Johns Hopkins Hospital influenza bacilli were rarely found. This conclusion was reached not only from the study of culture and smears but from the most minute survey of the stained sections, in which any considerable number of influenza bacilli could not be overlooked…Indeed it appears probable that some other form of living virus not recognizable by our microscopic methods of staining, and not to be isolated or cultivated by methods at present in use, must be the cause of the epidemic.”
The puzzle of the 1918-1919 epidemic would persist well beyond the era of bacteriology. In 1996, after the advent of virology and genetic science, medical scientists began to isolate the 1918 influenza genome from archived lung tissue of a victim. The sequencing was accomplished by 2005.
The Flu as an Epidemiological Model
The 1918-1919 outbreak has continued to intrigue investigators at Johns Hopkins and elsewhere. They have given the war-related outbreak new purpose: understanding and preparing for deadly flu pandemics in the present. The post-9/11 world has created anxieties about the possibility of biological warfare. Outbreaks of SARS and H1N1 have also reminded Americans that the spread of unusual strains of influenza remains a real and frightening possibility. As the biggest flu pandemic in modern history, the 1918-1919 outbreak’s numbers and movement have become useful models for thinking about potential future scenarios. In 2006, Derek Cummings and Donald Burke of the Bloomberg School of Public Health mined data from the outbreak and used computer technology to map its movement and magnitude. They were developing a tool for thinking about the potential movement of 21st-century avian flu pandemics across the globe.