Dust with a side of disease
Written by: Grace Lloyd
Dust and sandstorms are natural phenoms which distribute large quantities of dust from dessert topsoil [1-3] typically occurring in regions shown in figure 1. Each year the storms are estimated to circulate 0.5-5 billion tons of dust throughout the atmosphere [4]. The effects of these storms are felt thousands of kilometres away from the source and as deserts are ridden with a multitude of microorganisms rich in biodiversity [2-4], this means trillions of microbes can travel around the globe through dust events.
Large scale events are typically met with large scale consequences and dust is no exception to this. 2017 estimates show that particulate matter from desert dust is responsible for up to 600,000 deaths per year [5]. But what about all those hitch-hiking microbes?
There is a well-established link between dust storms and meningitis outbreaks specifically throughout North Africa, in what is dubbed as the “meningitis belt” [1, 2]. These outbreaks are estimated to affect another 200,000 people per year.
It has proven difficult to definitively link other pathogenic outbreaks to dust storms.There are numerous diseases associated with dust events. Two bacteria species Acinetobacter calcoaceticus and Corynebacterium aquaticum, which cause respiratory and urinary tract infections, were collected from dust storms in Mali, North Africa. In the U.S.A. Pseudomonas aeruginosa, a bacterium known to cause fatal infections in burn patients and Coccidioides immitis, a fungal infection which causes Valley fever [1, 4], have both been identified in the atmosphere after local and international dust storms [2].
It is speculated that the H5N1 avian influenza outbreaks, which riddled Japan and South Korea throughout 2003-2005, were further spread by an increase of the virus load during dust storms around Asia. Type A influenza concentrations have also been detected in air samples from Taiwan after local dust events [4].
Outside of human pathogens, outbreaks of fungi have been recorded in Seafans throughout the Caribbean [4] and locus populations in India [2]. Not to mention the multitudes of fungi outbreaks in crops around the world, transported via dust [2, 4]. The transmission of foot and mouth disease, a viral infection, has been well documented throughout Europe [4]. Estimates suggest cattle 300km downwind from the source developed the disease [2].
As you would expect, a strong immune response can mitigate some of the damage done by these pathogens. However, dust particles are known to worsen immunity in humans. Particles have been shown to damage cells [2] and trigger inflammation when inhaled [5]. The build-up of inhaled dust over all weakens any immune response [1] and is accompanied by varying short-term and long term effects. The severity of long term effects can range from the development of asthma and bronchitis to irreversible airflow obstructions [2].
The good news is the effect dust storms have on human health can be mitigated fairly easily. Warning systems, such as dust storm forecasting can significantly aid public health decision makers [5], the United Nations stated such precautions were vital in the preservation of human health [6]. Preliminary warning systems are in place currently however researchers are urging for increased accuracy and accessibility [4, 5, 7].
The ecological consequences of dust storms are much harder to alleviate and plan for. Within the scientific community, our current knowledge of this area is considered insufficient [2, 4]. Future research could enhance or change, our responses to dust events throughout the world.
References
1. Goudie, A.S., Desert dust and human health disorders. Environ Int, 2014. 63: p. 101-13.
2. Griffin, D.W., Atmospheric movement of microorganisms in clouds of desert dust and implications for human health. Clin Microbiol Rev, 2007. 20(3): p. 459-77, table of contents.
3. Initial. How Can You Catch Disease Through The Air? 2018 [cited 2020; Available from: https://www.initial.com/au/how-you-catch-diseases-through-air/.
4. Behzad, H., K. Mineta, and T. Gojobori, Global Ramifications of Dust and Sandstorm Microbiota. Genome Biol Evol, 2018. 10(8): p. 1970-1987.
5. Jusot, J.F., et al., Airborne dust and high temperatures are risk factors for invasive bacterial disease. J Allergy Clin Immunol, 2017. 139(3): p. 977-986 e2.
6. Nations, U. Convention to Combat Desertification, Sand and Dust Storms. Sand and dust storms; Available from: https://www.unccd.int/actions/sand-and-dust-storms.
7. Schweitzer, M.D., et al., Lung health in era of climate change and dust storms. Environ Res, 2018. 163: p. 36-42.