Hundreds of microorganisms, including pathogens, discovered 3,000 meters above Japan

A paper has reported that in a survey of 10 flights flying near the atmospheric boundary layer (1,000 to 3,000 meters above sea level) over Japan, hundreds of species of bacteria and fungi were collected from the atmosphere at altitudes of several thousand meters.

Microbial richness and air chemistry in aerosols above the PBL confirm 2,000-km long-distance transport of potential human pathogens | PNAS
https://www.pnas.org/doi/abs/10.1073/pnas.2404191121

10,000 Feet Up, Scientists Found Hundreds of Airborne Germs - The New York Times
https://www.nytimes.com/2024/09/09/science/high-altitude-germs.html

A research team led by Dr. Xavier Rodeau, a computational ecologist at the Barcelona Institute for Global Health, was investigating the causes of a disease called Kawasaki disease .

Kawasaki disease, first reported by pediatrician Tomisaku Kawasaki in 1967, is seen in infants and young children of East Asian descent, including Japanese, aged 4 or younger, and is characterized by symptoms such as fever, bloodshot eyes, red lips, rash, changes in the hands and feet, and swollen lymph nodes. The cause of Kawasaki disease is unknown at the time of writing, but Dr. Rodeau suspected that the outbreak of Kawasaki disease might be related to winds from northeastern China, so he took a Cessna plane to an altitude of 3,000 m above Japan and analyzed the samples.

They found high concentrations of a rare mineral called hafnium , likely from a Chinese mine, as well as over 266 fungal spores and over 300 different types of bacteria attached to tiny dust particles.

Many of these microbes came from plants and soil, but some were also found to live in the human body. Some of them were estimated to have traveled more than 1,900 km, yet still survived and were able to grow in the laboratory.

Dr. Rodo points out that the microorganisms discovered may contain potential pathogens. Specifically, about one-third of the bacteria could be pathogenic to humans, but he is cautious, saying, 'We have no evidence yet that these microorganisms actually fall to the ground and cause disease in humans.' In fact, the number of pathogens in the air above is much less than the number of pathogens in the breath of an infected person in a poorly ventilated building.

Dr. Rodo points out that the results of this study do not solve the mystery of Kawasaki disease, but it is possible that a pathogen carried by the wind high in the atmosphere could be causing some sort of illness in children.

'We were surprised at how many pathogens we found,' said David Schmale, an aerospace biologist at Virginia Tech who was not involved in the study. 'But these microbes may just be relatives of pathogens and be harmless. The best way to find out if they are pathogens is to infect human cells or lab animals.'