TO TELL a dusty day from a deadly one, you might need to take to the skies.
The Coccidioides fungus lives in the desert soil of the Southwest US and Mexico, but on dry, windy days it can get kicked up into the air. Inhaling a single spore can cause pneumonia – or worse. A drone designed at the University of California, Merced, aims to be a nose in the sky, searching for the airborne fungus to warn people when levels are high.
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The fungus infects an estimated 150,000 people a year, causing a flu-like condition called valley fever. If properly diagnosed, valley fever can be treated with antifungal drugs, but little is known about how the spores spread through the environment, or how to stop this happening. The goal of the Merced project is to find out. The team wants to test for spores in flight, mapping their flow and potentially warning communities to stay indoors or wear masks on the most dangerous days.
“We want to be able to answer the question of when it is uplifted into the atmosphere, by what means the fungal spores travel, and at what point they may interact with humans,” says team member .
In early March, the team flew their sampling system for the first time above pools and grasslands in a reserve on the university campus.
The current version of the drone flies up to an altitude of 80 metres, then circles a predefined coordinate at a 200-metre radius. During the flight, a pump sucks in up to 20 litres of air, trapping particles in a filter for analysis on the ground later. Other sensors record ambient conditions like pressure, temperature and humidity, which are needed to calculate the movement and density of particles.
Analysing the samples is still a work in progress. “We’ve been able to extract DNA from UAV-collected samples,” team member says. Now the team is working to classify microbial groups and to see how they vary across space and time as the drone flies. The ultimate goal is to do this in real time, issuing warnings when spore count is high.
And as California keeps drying out, those warnings may become more necessary. Drier, looser soils make it easier for particles to find their way into the air, and these conditions are more likely with climate change and the current El Niño.
“For decades, valley fever has plagued California’s Central Valley, and the illness is even more widespread as the state faces its fourth consecutive record dry year,” said of the US House of Representatives, who toured the team’s lab in 2014. “I applaud UC Merced for recognising this issue and using their drone technology to collect data.”
“Valley fever has plagued California’s Central Valley, and it is more widespread as the state dries”
Hard to find
But one worry is that the fungus might not cooperate, says of the Valley Fever Center for Excellence at the University of Arizona in Tucson.
Previous tests to hunt down spores that used air pumps on the ground have succeeded, but only barely, he says. While they did detect small amounts of fungus, one of the researchers also became sick. The fungus can easily find humans, but its hard for humans to find and study the fungus.
That may be because the spores, although very infectious, are so rare. “The number I use is roughly a 3 per cent chance of inhaling the spore for a human every year in the endemic region,” Galgiani says. In a few minutes, an adult breathes in more air than the Merced drone does in its flight, meaning the tests will have to either be very sensitive or that they will only work when spore levels are unusually high.
But the value of finding valley fever with a drone out in the wild would be considerable, Galgiani says. Currently, we have a hard time studying the disease outside of the people who show up in clinics. And these don’t give a very detailed picture because only about a third of those exposed to spores develop serious symptoms, and because many of them are misdiagnosed with flu instead of valley fever.
“It would be a great advance if they find it,” says Galgiani.
(Image: Justin Sullivan/Getty Images)
This article appeared in print under the headline “Drone sniffs the skies”
