Though TB infection rates in the US are now at historic low, it is easy to forget what a tremendous decline that has been. From about the mid-1600s to the mid-1900s, TB was consistently one of the leading causes of death, often the leading cause of death, in Western Europe and the US. One thing to keep in mind is just how drastically mortality has changed in the last 100 years of so. Comparing causes of death from 1900 and 1997^1 we can see that infectious diseases (TB leading the pack) were easily the most common cause of deaths in 1900. The modern numbers show infectious disease barely cracking into the top 10, which is dominated by heart disease and cancer.

For another comparison, in 2013 the mortality rate per 100K and percentage of total deaths in the US for heart disease and cancer were 193 (23.5%) and 185 (22.5%), respectively.^2 In the UK, the mortality rate from TB in 1900 was 133, down from 385 in 1838,^3 while in the US, the mortality rate in 1900 was 201, and TB was the number one cause of death.^4 In total numbers, this meant about >75K deaths in the US and >60K in the UK, annually, during this period. A 1907 US Census report stated

Tuberculosis is easily the first in importance among all the causes of death, and far exceeds in its mortality any other of the infections disease with whose prevention and restriction public health services are concerned.

As the early 19th century UK numbers show though, by the start of the 20th century TB infections had already significantly declined. Dubos, in his seminal 1952 book, The White Plague: Tuberculosis, Man, and Society, estimates in the early 19th century the TB mortality rate in US cities in the Northeast was as high as 400 per 100K.^5 Murray has estimated that the mortality rate peaked in Western Europe and the US around 1800, when it may have been as high as 1000/100K and as much as 30% of all motality in England and Wales could be attributable to the disease.^6 We do know that death records from town and cities in New England and NYC showed an increase during the latter half of the 1700s. The percent of all deaths attributed to TB in Brookline, MA, for example, increased from 16% to 27% between 1760 and 1812. In NYC, the TB mortality rate topped out between 1810-1815, when the rate was consistently >25%.^7

To shift away from a Euro-/Ameri-centric perspective, in late 19th Century Japan we see similar epidemic mortality rates. Between 1886-1899, the TB mortality was 132/100K, constituting more than 6% of all deaths in Japan during this time. This totals up to more than 700K deaths, surpassing the 2% and 1.6% percent of deaths attributed to dysentery and cholera. Keep in mind that the 1886 data includes a cholera epidemic.^8

The cause for the climbing rates through the 17th & 18th centuries, and the astoundingly high rates through out the 19th and into the early 20th centuries is fairly easy to explain. This was a time of rapid urbanization, which saw large numbers of people crowding into cities without attendant changes in housing or hygiene to accommodate them. Tuberculosis is a profoundly infectious pathogen, and the close quarters of urban centers during this time were terrific incubators for the disease, which could then spread far and wide. The decline is murkier. A very famous idea was that of Thomas McKeown, who theorized that it was not improvement in medical care/prevention that led to the decline of TB, but improvements to the environment. While it is true that non-surgical treatments for TB did not come along until streptomycin in the the 1940s and isoniazid and rifampin in the 1950s, McKeown's Thesis has been savaged in more recent decades. The current consensus looks towards a more multifactorial cause for the declining rates, with improvements not only in the environment and diet, but also changes to medical care, and the growth of the understanding of infectious diseases processes.

^(1 Cohen, ML 2000 Changing Patterns in Infectious Disease. Nature 406: 762-767)

^(2 CDC 2014 Deaths, Percent of Total Deaths, and Death Rates for the 15 Leading Causes of Death: United States and Each State, 1999-2013. National Vital Statistics System)

^(3 Worboys 2010 “Before McKeown: Explaining the decline of TB in Britain 1880-1930” in Tuberculosis Then and Now: Perspectives on the History of an Infectious Disease, eds. Condrau & Worboys)

^(4 US Census Bureau 1909 Mortality Statistics, 1907)

^(5 Dubos & Dubos 1952 The White Plague: Tuberculosis, Man, and Society)

^(6 Murray, JF 1989 The White Plague: Down and Out, or Up and Coming? American Journal of Respiratory and Critical Care Medicine, 140[6])

^(7 Holmberg, SD 1990 The Rise of Tuberculosis in America before 1820. American Journal of Respiratory and Critical Care Medicine, 142[5])

^(8 Johnston, W 1995 The Modern Epidemic: A History of Tuberculosis in Japan)

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