Inflammation of the Climate: The Impact on Gastrointestinal Infections

Inflammation of the Climate: The Impact on Gastrointestinal Infections

Parul Sarwal, M.D. George M. Abraham, M.D., M.P.H., F.A.C.P., F.I.D.S.A.

The United States ventured to return to the Paris Climate Agreement this January, a month that saw warmer-than-average temperatures in most parts of the country. The average global temperature today is 1 degree Celsius higher than before the industrial revolution of the last century. While this statistic beguiles the gravity of the climate crisis, extreme weather events certainly do not - as demonstrated by the increasing frequency of heat waves and floods, among other natural disasters. The 2020 Atlantic hurricane season witnessed the greatest number of storms in recorded history in the shortest duration of time; so much so, that the National Hurricane Center ran out of human names for the storms, needing to turn to the Greek alphabet for Tropical Storm Beta, the cyclone that affected the southeastern US this past September.

One of the myriad corollaries of harsh weather is an upsurge in infectious diseases, primarily gastrointestinal (GI) and hepatic. Studies have consistently demonstrated an association between temperature variations and GI infections. A recent review by Australian researchers confirmed that temperatures warmer than the usual baseline are associated with more frequent bacterial GI infections, which is compounded by an increase in humidity and precipitation. Campylobacter and Salmonella infections peaked in Scotland in July according to one study. This brings to mind the “gastroenteritis season” in July and August every year during my medical school training in India — rows of extra hospital beds in the hallways festooned with bags of IV fluids.

A heat wave is defined by the World Meteorological Organization as five or more consecutive days of prolonged heat wherein the daily maximum temperature is at least 9 degrees Fahrenheit (5 degrees Celsius) higher than the average maximum temperature. Scientists in Switzerland reported a nearly 5% increase in GI infections and resultant hospitalizations for every additional hot day during heat waves – an effect not observed during spells of cold weather. The year 2018 saw one of the longest heat waves in the United Kingdom. This prompted water treatment agencies to offer Legionella risk assessments to prevent potential outbreaks. While not primarily a GI infection, Legionnaires’ disease can often cause diarrhea, and its outbreaks have been partly ascribed to climate variations by the scientific community. This is perhaps due to its propensity for spread via internal climate control systems. Thus, it is important to note that external climate change can cause increased disease spread via internal climate change machinery. In the same vein, we are presented with uncharted challenges with respect to sanitation and clean water. There has been a resurgence of hepatitis E virus in endemic areas due to increasing population densities as well as the increased frequency of flooding and drought, impacting access to safe drinking water. Further, variations in temperature and carbon dioxide levels are postulated to have effects on mutation patterns in Rotavirus and hepatitis A virus, both of which have fecal-oral transmission.

The 2019 Lancet Countdown report describes how environmental suitability for the transmission of Vibrio species has increased because of climate change. Vibrio species are implicated in a range of infections, including cholera, and are found in brackish waters. Variables such as sea surface temperature and salinity have been reported to affect Vibrio infections. There has been nearly a 30% increase in the coastline area suitable for species of non-cholera Vibrio in northeast US in the 2010s, compared to the 1980s. Increasingly favorable conditions for coastal V. cholerae sensu lato in various regions around the world have allowed it to thrive globally.

As the human footprint on the planet grows, wild habitats shrink and we encroach upon their borders, enabling interspecies transmission of pathogens that then amalgamate into new and terrifying disasters – the COVID-19 pandemic being one of the latest in a long line of these infectious harbingers. There is thus a growing need for physicians, as community leaders, to join the current debate on climate change, because it is directly impacting our patients and our planet. If we fail to speak up, we would be guilty of our silence, as Martin Niemöller’s quote goes:

First they came for the Communists and I did not speak out because I was not a Communist

Then they came for the Socialists and I did not speak out because I was not a Socialist

Then they came for the trade unionists and I did not speak out because I was not a trade unionist

Then they came for the Jews and I did not speak out because I was not a Jew

Then they came for me and there was no one left to speak out for me

Dr. Parul Sarwal is a PGY-III internal medicine resident at Saint Vincent Hospital. Dr. George Abraham is Chief of Medicine at Saint Vincent Hospital, President-Elect of the American College of Physicians and Chair of the Massachusetts Board of Registration in Medicine.

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