Global Warming and the Spread of Disease: We’re Seeing it Now

“God has cared for these trees, saved them from drought, disease, avalanches, and a thousand tempests and floods. But he cannot save them from fools.”
—John Muir

In my book “Comprehending the Climate Crisis,” chapter five addresses the consequences of global warming. The title of the chapter is “Global Warming and its Devastating Effects.” In one subheading, I address the spread of disease. In fact, I previously posted an excerpt from this chapter and you can read it here if you’re interested. Briefly, I pointed out that as global warming continues, disease vectors such as mosquitoes are going to extend their territories, and diseases such as malaria and West Nile virus are going to affect greater numbers of people in regions previously safe from such diseases.

Sadly, we are seeing the evidence: that is precisely what is happening. The Centers for Disease Control and Prevention (CDC) is reporting that as of August 21, 2012, West Nile has been detected in 47 states within the US in either birds, humans, or mosquitoes. A total of 1,118 cases have been documented with 41 deaths among them. Continue reading

Global Warming and the Spread of Disease

My book Comprehending the Climate Crisis has sold more than 500 copies. That may not sound like much, but apparently it’s enough to allow me to achieve the Star Books designation from the publisher, iUniverse, as part of its awards program. For the application process I need to find some excerpts that can give a feeling for the book and  also stand alone well.

I’ve looked the book over and have found a few sections that I think can serve as excerpts which fit the bill. I’m going to post a few in the next little while so you can get a sense of the book and let me know if these excerpts work well or not. Please feel free to leave comments.

This particular excerpt is from Chapter 5 on the consequences of global warming. This segment specifically addresses the increased spread of disease.

Many diseases are passed on from one living organism to another through direct contact. Rabies can come from animal bites, Lyme disease comes from insects, and many bacteria and viruses can thrive almost anywhere, so that simple contact is enough to become infected—one of the reasons we’re always being told to wash our hands. The mode of transmission for communicable diseases is known as the vector. As global temperatures increase, in many regions, the geographical areas where these vectors live will expand.

Let’s look at malaria as one example. Unless you live in or travel to certain specific regions on the planet, it’s unlikely that you will personally be at risk to contract the disease, but malaria is a massive problem on a global scale. According to the World Health Organization, about 250 million cases of malaria occur each year, resulting in nearly 1 million deaths among them, most occurring in children under the age of five. Malaria is spread through mosquito bites. You may have heard about the importance of supplying developing nations located in the tropical regions where the disease is endemic with enough mosquito nets for their living quarters to help stop the spread of this disease. The mosquitos don’t get the disease themselves, but they carry it from person to person; they are the vector in this case.

In malaria, the name of the bacteria is Plasmodium, and there are five different species of it that can infect humans. If a mosquito bites someone infected with malaria, then it will ingest some of the bacteria living in the red blood cells of that infected person. Once a mosquito has ingested these parasites, the parasites will develop inside the mosquito over a week or so without harming it. But once the mosquito bites another victim, the parasites are passed on via the bloodstream. Over weeks to months, the Plasmodium bacteria go through their life cycle, initially in the liver of the victim and then ultimately multiplying in the red blood cells, where another mosquito can ingest them, allowing the cycle to continue with the next mosquito bite. Ultimately, malaria can cause fever, hallucinations, and even coma or death.

Obviously, the best way to deal with this disease is by preventing it in the first place—thus the importance of such simple measures as mosquito netting. If people know they will be traveling to parts of the world where malaria is endemic, they can take oral medications to prevent getting the disease in case a mosquito bites them. These preventive medications are known as prophylactic drugs. They are started before the trip so that they’re present inside the traveler and ready to disrupt the life cycle of the parasite if he or she is ever exposed from a mosquito bite. Treatment once someone develops malaria involves even more powerful medications than the prophylactic drugs and usually requires hospitalization.

Malaria is generally thought of as a tropical disease. As you can well imagine, when global temperatures rise, the area where the mosquito vector can thrive will expand, increasing slowly into latitudes farther away from the equator, regions of the planet that have always enjoyed more moderate temperatures. When a frost occurs, adult mosquitoes as well as their larvae are killed, but with warmer global temperatures, the frost line will gradually move farther away from the equator. As a result, there won’t be as much of a distinction between the tropics and these more moderate latitudes, and the mosquito vector will easily extend its territory and find a new home. The areas where malaria is endemic will expand into regions where malaria has never been considered a health concern, with more cases added to the list and more deaths as a result. And an expanding mosquito territory isn’t the only way that global warming will increase the risk of the spread of malaria: hotter weather will lead to longer summers and, therefore, longer mosquito seasons; higher temperatures cause shorter mosquito breeding cycles; female mosquitoes tend to bite more with higher temperatures; and the heavy rains that result from global warming will create more ideal conditions for mosquitoes to breed since they like stagnant water.

Malaria is only one example of the possibility of disease spread due to global warming, but it shouldn’t be too difficult to appreciate that the threat of many others exists as well, all as a result of the climate crisis. And these examples aren’t restricted only to tropical regions in remote parts of the planet. The Centers for Disease Control and Prevention (CDC) in the United States has confirmed that vector-borne communicable diseases in North America are also changing in both distribution and frequency. Other vectors, such as ticks and mice, are expanding their territories and carrying their diseases into broader territories just like mosquitoes are. Some examples in North America include Lyme disease, Rocky Mountain spotted fever, and certain types of encephalitis, a serious and potentially disabling or even fatal viral infection of the brain. And since global transport is so rapid today, with a flight to Europe or Africa taking only a matter of hours, diseases that were previously considered endemic to faraway regions of the world, such as West Nile virus, can truly become global problems in the present day all too easily.