Global Warming & the Spread of Infectious Diseases

Human health is linked to the health of the environment, including its plants and animals (yes, insects are classified as animals: Kingdom Animalia > phylum Arthropoda). Infectious diseases in humans are caused by viruses, bacteria, parasites, or fungi, and transmission is via one of four routes:

1. Direct human to human transmission is often via contaminated body fluids: fecal matter, saliva, respiratory droplets, vaginal fluids, sperm, and blood (HIV/AIDS, tuberculosis, measles, STDs).
2. Direct animal to human transmission is typically via insects and mammals (rabies). Indirect, vector-borne transmission between humans and humans is usually insect- (malaria, dengue fever, yellow fever) and water-borne (cholera, Giardia).
3. Indirect water-borne infections are usually transmitted between humans via ingested contaminated drinking water or food, or through immersion (Leptospirosis, Schistosomiasis).
4. Indirect, vector-borne transmission between humans and mammals is usually via insects (bubonic plague, Lyme disease) or the urine and feces of infected rodents (Hantavirus).

Each pathogen, animal vector, and host has an optimal climate in which they thrive with warm, moist temperate, subtropical, and tropical environments being the best. Global warming has increased, and will continue to increase, both temperature and precipitation worldwide leading to a proliferation of many infectious diseases. While this trend—the increase in infectious diseases—is predictable, the exact type and location of an emerging disease is not. It’s likely you will be exposed to an infectious disease where there is no historical data. To this end, you should take care to protect yourself by ensuring good personal and expedition hygiene, taking precautions against insect-borne diseases (see this blog article for details), and avoiding potentially infectious animals and their habitat. Keep in mind that although the Centers for Disease Control (CDC) and the World Health Organization (WHO) are monitoring the situation worldwide, (and it is worthwhile to visit their sites to see if the area you live, or intend to visit, is endemic to a specific disease) specific outbreaks are impossible to predict. Be cautious and take precautions.

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