Pathogens ride high-altitude winds over vast distances

Pathogens traveling on the wind may be more common than we realize. A recent study has revealed a surprising discovery – potentially harmful microbes, including antibiotic-resistant bacteria, travel vast intercontinental distances on high-level winds.

The study, which is the first of its kind, focused on data from tropospheric aircraft surveys.

Scientists led by Professor Xavier Rodó at the Barcelona Institute for Global Health uncovered an unexpected diversity of bacteria and fungi, some of which are pathogenic to humans. 

“Around 30-40% of the microbes were potentially pathogenic species, either well-recognized human pathogens or opportunistic pathogens,” noted Professor Rodó. This can affect people with weakened immune systems.

High-flying pathogens

While concentrations of microbes in the air are too low to cause immediate illness, Professor Rodó warned that the real concern lies in the potential for these airborne microbes to introduce antibiotic-resistant genes into new environments.

“The genes are transported in living organisms, so they have a greater likelihood of passing once the aerosol settles,” added Dr. Allen Haddrell of the University of Bristol, who was not involved in the study.

The resilient microbes were found covering distances up to 1,200 miles, attached to dust particles in a study conducted over Japan. 

These dust particles, originating from farm fields in northeastern China, transported more than 300 species of bacteria and 260 types of fungi across the skies. Similar wind patterns likely carry microbes across other regions of the globe.

Pathogens and winds of resistance

The sheer number of microbial species surprised the researchers, as their initial goal was simply to analyze the chemistry of the dust particles. 

“This is a word of caution that we should be changing our view of the air,” said Professor Rodó. He pointed out that these microbes endured extreme environmental conditions, protected by the dust particles they traveled with.

Some of the species identified include well-known human pathogens such as E. coli, Staphylococcus saprophyticus, and Clostridium difficile. 

Protected from ultraviolet light and dehydration, these pathogens remained viable and capable of replicating after long journeys.

Pathogens in the wind samples

Dust samples were collected at altitudes between 0.6 and 1.9 miles above Japan, beyond the planetary boundary layer (PBL). At these altitudes, winds travel faster and farther due to reduced friction with the ground. 

Chemical analysis confirmed the dust’s long-range origin, containing rare elements such as zirconium and hafnium, which were traced to agricultural regions in China.

“The chances of getting an infectious dose (via high-level winds) must be considerably less than when encountering an infected person on an airplane,” noted Professor Chris Thomas from the University of Birmingham.

However, Professor Thomas noted that the dust and chemicals accompanying the microbes may pose a greater health risk as air pollution.

What does this mean for humans?

Though the immediate risk of infection from these high-altitude travelers is low, the presence of antibiotic-resistant microbes raises concerns about global health. 

Professor Rodó emphasized that the findings reveal an underappreciated dimension of antibiotic resistance. The experts concluded that the troposphere could act as a reservoir and long-distance transporter of various microbial species, including harmful ones.

This highlights the potential for airborne pathogens to contribute to antibiotic resistance, posing significant public health concerns that require further investigation. Understanding these dynamics is crucial for developing strategies to combat the spread of resistant bacteria.

Pathogens and antibiotic resistance

The research opens up new questions about the spread of antibiotic resistance via wind-borne pathogens and dust particles.

Dr. Haddrell warned that this is going to be a problem over the long term as more resistant strains of bacteria may find new environments in which to thrive.

The study also raises broader concerns about air pollution, with dust and chemicals contributing to airborne health risks.

While the airborne pathogens may not pose an immediate threat to most people, their ability to survive long-distance travel and carry antibiotic-resistant genes should prompt further investigation. 

The study adds yet another layer of complexity to our global ecosystem, highlighting the need for ongoing research into the invisible travelers riding the wind.

The study is published in the journal Proceedings of the National Academy of Sciences.

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