Desert Wind

Desert Wind was the name given to a mild airborne infection endemic to the rural deserts of Po-Powai on Powai Nui. It exclusively afflicted Matoran, Toa, and Turaga.

History
The microbes which caused Desert Wind were likely created by one of the Makuta using viruses and liquid Protodermis during the early days of the Matoran Universe. For unknown reasons, they were not spread around the Matoran Universe, but instead settled exclusively on Powai Nui in the western chain of the Southern Islands.

On Powai Nui, Desert Wind became widespread, due both to it's high contagiousness and strikingly low fatality rate. It was among the first diseases to be recognized by the island's early Matoran tribes, and was seen more as a nuisance than anything particularly dangerous. Some tribes, particularly those composed of belligerent Ta-Matoran, attempted to weaponize it by harvesting the cocoons that contained it and sneaking them into the villages of opposing tribes. This practice proved to be ineffective, however, especially outside of the island's desert regions.

After the formation of the Powai Nui Governing Coalition was formed, Ko-Powai saw a period of rapid scientific and technological development. One of the results of this period was Serpex, a substance invented by a Ko-Matoran of the same name which could cure a myriad of illnesses, disease, and parasitic infections which were common on the island. Desert Wind was among the first Powai Nuian diseases to be assailed by widespread use of Serpex, and numerous strains of it were made extinct. Those that survived began to develop resistances to Serpex, allowing them to persist through the onslaught. However, due to the properties of the microbe, those that were resistant to the substance also became less infectious.

Eventually, due to random chance mutations, strains that had been wiped out by Serpex began to reappear, which were much more infectious than before. With the Powai Nuians' recent advancements in medical technology and treatment, however, they did not prove much more of a threat than their ancestors had. These more infectious strains were repeatedly wiped out by Serpex and brought back by resistant strains, resulting in what was essentially an eternal deadlock between the disease and the island's inhabitants.

Causes
Desert Wind was caused by a group of airborne microbes endemic to Powai Nui which had multiple ways of finding and infecting hosts. These microbes were colonial, and would group up to burrow into sand and form small habitats known as cocoons. Cocoons were pustule-like formations made of sand stuck together with adhesive compounds, and were generally an inch or less in diameter. They were designed to release copious amounts of microbes when broken, and were usually broken by being stepped on by travelers.

The microbes were able to survive in air away from nutrients by forming a protective endospore and slowing down it's life processes. Due to a flaw in it's design, these endospores could be prematurely opened by contact with a large enough amount of water. Because of this, they rarely survived in humid or rainy environments. Those microbes that did survive being airborne could infect Matoran through inhalation.

Symptoms
Once inside a Matoran's lungs, Desert Wind microbes began to release adhesive compounds to create a smaller cocoon and expelling water out their new abode. This irritation caused coughing, as the Matoran's rudimentary immune system attempted to expel the invader out of the lungs. Coughing for long enough could cause these adhesives to be ejected into the throat, where they would stick to it and congest it. While these symptoms were fatal in rare cases, the infection would usually be fought off before they could progress to such a point.

Prognosis
Desert Wind was naturally not a fatal disease, and killed far less than 1 percent of all of it's hosts. All recorded cases of death while infected with it were due to other causes in conjunction with the disease, and as such the number of fatalities it has caused has always been disputed. A Matoran's immune system could usually invade the microbe's domain and destroy it within 1-3 weeks; if not, coughing would expel it.

Spread
Due to the properties of it's microbe's endospores, Desert Wind was incredibly rare in humid environments, and was most common in Powai Nui's hot and dry, especially Po-Powai. This attribute, along with it's symptoms, were the inspiration for it's name. Because of it's high infectiousness and ability to recreate more infectious strains after they are wiped out, it was the single most widespread disease on Powai Nui.

Trivia

 * Desert Wind took inspiration from several real-life diseases, most notably the common cold and anthrax.