New York (City). Board of health.

A devastating disease, poliomyelitis attacks the motor nerve cells in the spinal cord, often leading to permanent paralysis or, in the most severe cases, death. The pathogen causing polio was identified by Karl Landsteiner in 1908 as a filterable virus, but the carrier of the virus and mode of transmission remained topics for heated debate for many years. Although it was known to strike the wealthy as well as the poor, in the popular imagination, the disease was indelibly associated with filth, vermin, and the poor.

The poliomyelitis epidemic that struck in the summer of 1916 was one of the largest ever in the United States, with over 27,000 cases reported from 26 states -- 8,900 in New York City alone -- and a mortality rate approaching 25%. In response, the emerging class of health professionals in New York intervened with a broad epidemiological and public health campaign using both the legal recourse available to them by virtue of new public health legislation and the old nostrum of moral suasion to convince the vulnerable into cleanliness and salubrious habits.

The center of polio research at the time was New York's own Rockefeller Institute, and drawing upon this expertise, the Department of Health formed a committee to investigate the epidemiology of the disease and to find ways of limiting its spread. Initially, their focus fell on the poorer wards of the city, particularly on the Italian immigrant communities, and working within the dominant paradigm of disease as a product of filth, the Department of Health waged a public health propaganda campaign, sponsoring fly catching or rat killing contests in the belief that these would eliminate disease vectors. Stray pets -- also putative disease vectors -- were rounded up and slaughtered by the thousands.

At the height of the epidemic in July and August, near panic set in to the city, with hundreds attempting to flee for healthier locations and the Department of Health attempting equally hard to prevent the flight, stationing police along all of the major roads to prevent unauthorized persons from entering or departing. The paradoxical finding of the research, however, was that the incidence of polio infection was ultimately not directly correlated with conditions of filth, insufficient nutrition, overcrowding, uncleanliness, or the presence of vermin. Instead, it seemed to affect the poor less severely than the middle class, From a present day perspective, the majority of children in poor communities were exposed to the polio virus early in life when the effects of the disease were less virulent, while middle class children contracted it only later. The epidemic subsided as the weather cooled in the late fall and early winter.