The Modern World and Disease


Recently I’ve come to a sparkling realisation that the management of the environment and human health is very inexplicably linked. So maybe it should have been an obvious one, but the impact has only just hit me.

We are in living in a world that will only continue to be plundered, to be urbanised and continue to be developed. It becomes a massive fight to keep protecting and maintaining an area clear of human influence. Even now, the fight isn’t about establishing no man zones of pristine wetlands or areas, but minimising human use because it’s become impossible. It is no longer feasible to consider it possible to keep an area completely free of human impact.

A comprehensive review published in the past year by a team from the College of Global Change and Earth System Science of Beijing Normal Univeristy and School of Environment of Tsinghua University have pointed out every direct and indirect factor of human change as well as the role that the changing environment will play in transmission of human infectious diseases – vector borne, water borne, zoonotic, the whole conundrum.

Emerging infectious diseases of concern are Ebola haemorrhagic fever, Legionellosis and Lyme disease. The big three are also discussed – the reemerging Tuberculosis, AIDS/HIV and the bane of my life: Malaria.

The review brings to mind that infectious diseases actually rank first on the list of greatest threats to human survival and that fatalities from disease count for 25% of all deaths. Doesn’t that smack you in the face? We see war and murder and rather dramatic happenings in everyday news but I feel like there’s hardly any awareness of the sneaky killer that is the pathogen nor have we completely silenced the vaccination debate. It actually seems to be blowing up in the midst of ballooning outbreaks of re-emerging diseases (i.e. Measles in the US, Ebola in South Africa, Whooping Cough).

The hard truth is, as the world ages and as the human population evolves – climate change and the impacts of a developing social environment will facilitate the spread of disease.

With global warming, the rising sea level and sea surface temperature will increase the incidence of water-borne diseases such as cholera, still rampant in developing countries. Changing climate will also affect the spread of insect borne diseases as it influences the geographic distribution and shorten incubation period of pathogens which will favour the flourishing of Malaria and Dengue Fever. The unpredictable weather that we live in now brings with it extreme changes in temperature and an increased likelihood of natural disasters that will only propagate the spread of infectious disease. The sudden peaks in temperature in Summer and Autumn in QLD was thought to be the reason behind the outbreak of the Ross River virus.

The review details how temperature and humidity directly impact the life cycle of pathogens and their proliferation or extinction. Unfortunately for us, the way our climate seems to be heading is towards their advantage. They say the world’s temperature is only going up and with warmer temperatures and higher humidity come troupical pathogens like Hep E., Vibrio cholera and the continued evolution of Influenza – although that I feel like is gonna happen no matter what. Plus there’s greater risk of food poisoning with food being exposed to a warmer environment, increasing the chance of salmonella contamination.

If you thought we could escape from areas of such tropical expansion and head to somewhere cooler like Alaska or Iceland – be prepared to meet a totally different side of communicable disease with having to protect yourself against tick and rodent vectors. There’s just no escape.

Add that with the frightening way the human population is expanding and how we are greedily attempting to consume all of the world’s resources all at once and it kind of seems like we’re just feeding pathogen growth on purpose.

International travel and the global trade have carried pathogens from one side of the world to another allowing the fastest spread of disease in all time. Many studies have linked the large spread of SARS to travel and the close quarters of a plane don’t give leeway to avoiding The Person That Sniffles/Coughs. Global trade is definitely a source for bringing foreign hosts into the country with more than 70% of emerging infectious disease and new viruses triggered along the various trade routes.

Rapid expansion of development push suburbs and city edges into undeveloped areas of forests and wastelands which increase the contact between humans and pathogens whether via animal hosts or vectors. This increased exposure of humans and pathogen hosts facilitate the evolution of zoonotic disease and with areas of high residential density, there is immense risk of epidemics occuring. It doesn’t help that continued deforestation add to this exposure.

Right now it seems all doom and gloom doesn’t it? Or maybe it seems completely otherworldly from where you are sitting. In the safety of our houses and in the quiet of wherever we live, we feel totally immune to the health issues that we feel are a “developing country” problem where they’re plagued with poor health infrastructure and socioeconomic weakness. In actuality, we’re not all that far away from the same problems despite being sheltered under a first world system. The reach of tropical and vector borne diseases will only expand with the changing environment that we live in.

What needs to be done is to be aware of the effects an aging Earth is leading to and to structure our health system accordingly. To be prepared to face new emerging diseases and new epidemics with the growth of the population and the increasing urbanisation of the world.

To end this. It’s been a long two (three…?) weeks.

This is a review of a Review:

Wu X X, Tian H Y, Zhou S, et al. 2014. Impact of global change on transmission of human infectious diseases. Science China: Earth Sciences, 57:189–203, doi: 10.1007/s11430-013-4635-0

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