Medical practitioners have long made claims about what climates were beneficial for recovering from tuberculosis, but have rarely reached consensus. Hippocrates believed it was related to damp winds and changes in temperature, and made several claims about what types of winds were helpful and which were harmful. Notably, he accurately observed variations related to the season. Celsus advocated sailing (optimally to Alexandria). Pliny the Elder also looked on Egypt favorably, but also mountains and woods. Later physicians would variously suggest open air, dry air, moist air, sea air, warm air, cool air, forests, horseback riding, healthy diet, and exercise, among other treatments. These beliefs were based largely on anecdote, though some made assertions based on how endemic tuberculosis was to different areas and generalized effects of climate from that.

The degree that these treatments helped is debatable. I am aware of no modern consensus on humidity – some studies find that increased humidity slightly increases transmission, and others find humidity negatively correlates with tuberculosis incidence. However, there are some factors that may play a role in why so many physician advocated trips to different climates. ‘Open air’ and travel –by virtue of increasing sun exposure – could help by increasing vitamin D production, which can have an effect on the immune system. Air pollution is certainly linked with exacerbation of lung disease, and exercise can help improve lung function. Moving to a new location could give patients a sense of control over their disease, potentially reduce stress, and of course the placebo effect can be powerful – all of these factors could affect the immune system. To add to this, even without treatment the survival rate for secondary tuberculosis (what people would call consumption or phthisis) was around 50%, so with confirmation bias it would be easy for people to jump to conclusions about how effective their treatments were.

One notable factor related to patients moving to parts of the American West was the effect of altitude. While not universally acknowledged, the benefits of altitude led to a number of high altitude sanatoriums being established in the 19th century, and this held sway well into the 20th century before effective antibiotic therapies were established. Greater use of statistics and epidemiology supported this (though questionable studies still supported other assertions about the effect of different climates on tuberculosis). A doctor in 1917 commented on the benefits of moving to the American West (and particularly to Colorado), but argued that patients who were already especially frail should not attempt high altitude, and warned that returning to low altitude could cause rapid deterioration. The fact is that mycobacterium tuberculosis’s growth is highly dependent on oxygen, and lower oxygen at high altitude can slow the progression of the disease. With the rise of multidrug-resistant tuberculosis, the use of high altitude could even see a resurgence today.

As for the danger to healthcare workers – many would have already been infected with tuberculosis, which is spread through aerosols. The primary infection (often occurring in childhood in endemic areas) is usually relatively mild. The biggest danger is when the immune system is taxed or suppressed, allowing the latent infection to become active again and expand.

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Sources:

Watson, Robert Bruce. An Introduction th the History of Climate and Tuberculosis. MIT Department of Biology and Public Health Thesis (1928).

Grant, RS. Tuberculosis and Climate. J Natl Med Assoc. (1918) Jan-Mar; 10(1): 18–21.

Sarkar, Srijata; Rivas-Santiago, César E; Ibironke, Olufunmilola A; Carranza, Claudia; Meng, Qingyu; et al.Season and size of urban particulate matter differentially affect cytotoxicity and human immune responses to Mycobacterium tuberculosis. PLoS One; San Francisco Vol. 14, Iss. 7, (Jul 2019): e0219122. DOI:10.1371/journal.pone.0219122

Lestari P, Sustini F, Endaryanto A, Asih R. Home humidity increased risk of tuberculosis in children living with adult active tuberculosis cases. Universa Medecina. (2011) Vol 30, No 3 .

Fernandes FMC, Martins ES, Pedrosa DMAS, Evangelista MDSN. Relationship between climatic factors and air quality with tuberculosis in the Federal District, Brazil, 2003–2012. Brazilian J Infectious Dis. (2017) Vol 21 (4); 369-375

Pérez-Padilla; Franco-Marina, F. The impact of altitude on mortality from tuberculosis and pneumonia. The International Journal of Tuberculosis and Lung Disease (2004), Vol 8(11); 1315-1320.

Murray, JF. Tuberculosis and High Altitude. Worth a Try in Extensively Drug-Resistant Tuberculosis? Am J Resp & Critical Care Med. (2014). Vol 189(4)

Good question! I think we ought to start with a bit of history of application of medicine here to understand where these ideas came from:

When I read this question, I thought of the conceptualization of the “Four Humors.” I think a lot of us who’ve studied anything about medicine, no matter how minor (believe me, my studies have been very minor), know very basically what this concept is. The best way I can think of describing it to someone who doesn’t really know what this is, though, is that this is the ancient understanding of how the body works. I typically hear of two dudes being credited for popularizing the idea of Humors: Hippocrates and Galen (mostly Galen). Those sound like pretty old names. They are: if we go with crediting Hippocrates, this idea formulated in like, 400BC. Yeesh. I can see why we see this as outdated and ineffective now.

The Four Humors are named as follows: Blood, Phlegm, Yellow Bile, and Black Bile. These are all essentially the belief of what is contained within the body, and how these things interact with the world around the individual; everyone is made up of the Four Humors, and regulation of them would mean that one is healthy. But how do they interact with the world? Well, the concept goes further. The Humors follow the elements, respectively: Air, Water, Fire, Earth. They follow the seasons, respectively: Spring, Autumn, Summer, Winter. Yes, it’s spiritual, but there’s also some logic behind it, too: this correlation implies that the Humors are changed, stimulated and effected by the external factors surrounding people. The time of day, the season... and the location around the individual.

Another related concept here is the Miasma Theory of Disease. If you’ve played a JRPG of any kind, you probably know what this term implies: bad air. Referring back to Hippocrates, he essentially thought that poor air quality could cause pestilence, and Galen expanded on this notion, with analysis on how much air can cause harm to the body, and even moving to state that bad air could be the cause of any disease (Jouanna, 2012).

Basically, combining these two concepts brings us to one conclusion: if you’re in a spot that’s considered to have bad air, and you have a disease correlated with your lungs, get the hell outta dodge. Your Humors need to find balance!

So that’s why we see people moving from place to place to “cure” their diseases. But... this is an ancient understanding of medicine, right? It was birthed so far back in the past. Surely there was better understanding in the time period we’re talking about? I mean, you’re talking about the 19th century, here. Actually, the Humors Theory was still thought to be pretty legit until the acceptance of the Germ Theory.

Going off of the 19th century theme, for me, cholera comes to mind as an example. “John Snow, one of the medical scientists in the mid of 19th century, came with the hypothesis that the main cause and spread of the cholera had not been bad air, instead, cholera could be spread in water, food or hand-to-mouth” (Kannadan, 2018). No, it wasn’t because Winter was coming: it wasn’t because of an imbalance in Humors, it was from micro-organisms! At first, this didn’t gain much rapport, because miasma was stealing the show: William Farr stated in the annual report on vital statistics in Great Britain (1852) that “the inverse association of cholera mortality with elevation above sea level confirmed the miasma theory as its cause” (Bingham, 2004). But after finding out that contaminated water supplies was a huge contributor in the spread of the disease (Kannadan, 2018), people began to really consider the theory of micro-organisms messing with them, rather than simply bad air.

So, to answer your question shortly, the sheer fundamentals for understanding health were different. And, therefore, methods for understanding how to cure diseases was different.

My bad if this is written a little poorly. I wrote this from my phone. Hope this helps shed some light on your question!

References/Further Reading:

Bingham, P., et al. (2004). “John Snow, William Farr and the 1849 outbreak of cholera that affected London: a reworking of the data highlights the importance of the water supply.” Public Health, vol. 118, no. 6. 387–394.

Duffy, J. (1993). “From Humors to Medical Science: A History of American Medicine.” Chicago: University of Illinois Press.

Jouanna, Jacques. (2012). “Air, miasma and contagion in the time of Hippocrates and the survival of miasmas in post-Hippocratic medicine (Rufus of Ephesus, Galen and Palladius).” Greek Medicine from Hippocrates to Galen. 119-136.

Kannadan, Ajesh. (2018). “History of the Miasma Theory of Disease.” ESSAI, vol. 16.