Giant storms filled with potentially deadly fungal spores are set to sweep across at least 11 US states this summer, with the worst conditions still weeks away.
Meteorologists and health experts have warned that dust storms in the Southwest will stir up dangerous fungal spores from the soil through September, potentially exposing millions to Valley fever.
This common illness is a lung infection caused by breathing in microscopic fungus particles called Coccidioides that live in dry soil frequently blown around by strong desert winds.
The spores turn into growing fungal cells that the immune system typically fights off, causing mild flu-like symptoms such as fever, cough and headaches in most patients, but severe infections can spread to the organs and bones and become fatal.
Illnesses could soon skyrocket as the Southwest, including California, Nevada, Arizona, Utah, Colorado, New Mexico and Texas enters the North American monsoon season - known for major thunderstorms and strong winds throughout the region.
These winds kick up huge walls of dust, also known as haboobs, from the dry ground right when the soil is at its driest. The combination of extreme heat and drought plus monsoon winds creates more frequent and intense dust storms carrying spores.
Valley fever cases tend to start peaking in October, a few weeks or months after the dust storms, because it takes time for the fungus to grow after people inhale the spores.
Forecasters have already issued air quality alerts this week as massive domes of high pressure trap smoke, haze and dust closer to the ground for people to breathe in.
A massive dust storm seen passing over Arizona. These storms can carry fungal spores which cause Valley fever
Forecasters said a high pressure system over the Southwest will cause serious air quality issues this week
Other states the Centers for Disease Control and Prevention (CDC) noted as being likely breeding grounds for Coccidioides include parts of Washington, Oregon, Idaho and southern Wyoming.
However, the health agency warned that the potential range of Coccidioides spores could spread over the entire western half of the US from Oklahoma, Kansas, Nebraska and the Dakotas to the Pacific Coast.
In June, AccuWeather's climate experts warned that the US could suffer from a 'mini-Dust Bowl' if the current El Niño weather pattern in the Pacific leads to a multi-year drought.
The historic Dust Bowl of the 1930s caused a major environmental disaster across the central US and Great Plains, bringing severe drought and destroying farmland.
A new Dust Bowl in areas where the CDC says it is possible for Coccidioides to live could expose tens of millions of Americans to the hazardous spores as dust storms intensify.
Researchers have found that cases of Valley fever have already risen dramatically in recent years throughout the Southwest, although experts are not sure exactly what is causing the infections to increase so fast.
A 2017 study in the journal Geophysical Research Letters noted that: 'In the Southwest frequented by dust storms, the infection rate of Valley fever has mysteriously gone up more than 800 percent from 2000 to 2011.'
The team from the NOAA Air Resources Lab and George Mason University also noted that there was a 240-percent increase in the number of giant dust storms in the 2000s compared to the 1990s.
The CDC notes at least 11 states at risk for Coccidioides fungal spores
Drivers and pedestrians can inhale the dangerous spores during dust storms, which are common in the Southwest between July and September
They concluded that the main cause was climate change, making the region drier. Moreover, tiny shifts in sea surface temperatures in the northern Pacific Ocean helped drive stronger winds and drier conditions that stirred up more dust.
Coccidioides grows naturally in dry, sandy soils in certain arid parts of the world - like the Southwest.
It thrives in alkaline-rich soils with hot summers, mild winters and low rainfall, and is generally harmless to most people most of the time unless it is being blown into the air and inhaled into the lungs.
While the CDC has called these infections rare, the agency admitted that: 'Some outbreaks happened in places where scientists did not expect the fungus to live.'
Celeste Saulo, Secretary General of the World Meteorological Organization, told BBC Science Focus: 'Sand and dust storms do not just mean dirty windows and hazy skies. They harm the health and quality of life of millions of people and cost many millions of dollars through disruption to air and ground transport, on agriculture and on solar energy production.'
Drivers caught in dust storms have been warned to keep windows shut and use the recirculated air conditioning to keep spores out
The CDC has urged anyone in the path of a dust storm this summer to stay indoors and shut all windows until the air is clear.
To avoid Valley fever, the Arizona Department of Health Services in Maricopa County said: 'Avoid dusty areas, such as construction [and] excavation sites, as much as possible. If you can’t avoid them, wear an N95 mask or respirator while at these sites.'
They added that locals should water down desert soil before spreading it to reduce the chances of it becoming airborne dust.
For drivers, the National Weather Service urged any driver who sees a dust storm coming to 'Pull Aside, Stay Alive,' meaning they should move their car off the road, shut the windows and use recirculating air conditioning if available until the storm passes.