Study warns airborne germs travel hundreds of miles across international borders

By Stephen Beech via SWNS

Germs can travel hundreds of miles through the air across international borders, reveals new research.

Potentially deadly bacteria – including E.coli and C.diff – travel at an altitude of up to 10,000 feet, say scientists.

Air samples taken at altitudes up to 3,000 meters (9,840 ft) above Japan showed the presence of many microbes transported hundreds of miles by aerosols originating in China.

Analysis of the samples revealed the presence of a vast range of viable bacteria and fungi transported by air masses originating more than 1,200 miles away, in regions enriched with fertilisers and pesticides.

The study, published in the journal Proceedings of the National Academy of Sciences (PNAS), reveals a new way in which human, animal and plant infections may travel to distant geographical regions.

The research team explained that infectious microorganisms – known as pathogens – can be airborne.

But little is known about the diversity of microbes that can survive at very high altitudes, where the conditions are harsh.

The research was led by the Barcelona Institute for Global Health (ISGlobal) in Spain.

Professor Xavier Rodó, of ISGlobal, said: “We know that above a certain point in the troposphere – called the planetary boundary layer – certain materials can be transported over long distances because the air in that region is isolated from the surface and there is less friction.

“But we did not suspect that viable microorganisms could be there also.

“Our study is unique in that we performed 10 tropospheric flights to examine microbial diversity at high altitudes, while most studies have been performed only a few meters above the ground or the ocean.”

Using a Cessna aircraft, Prof Rodó and an international team of colleagues conducted 10 air surveys between 1,000 and 3,000 meters above Japan, starting from Chofu airport near Tokyo.

All the flights were planned to follow wind currents coming from mainland Asia in what are known as tropospheric bridges, which connect air from distant regions of the world; in this case, air that uplifts in mainland China and then descends over Tokyo due to typical winter weather conditions.

For comparison, samples were also collected on the ground at Chofu.

A total of 22 aerosol filter samples, collected during two periods (February and April 2014), were analyzed for their chemical and biological composition.

DNA sequencing allowed the researchers to identify 266 fungal and 305 bacterial genera associated with the aerosols, some of which are potentially deadly for humans, other animals or plants.

Bacterial species including Escherichia coli (E.coli), Serratia marcescens, Clostridium difficile (C.diff), Clostridium botulinum, Haemophillus parainfluenzae, Acinetobacter baumannii and several Staphylococcus species were among those identified.

Fungal species such as Candida, Cladosporium and Malassezia – capable of causing disease in susceptible and immunocompromised individuals – were also identified.

By culturing some of the samples, the researchers showed that bacteria collected from the air remained viable and that some were resistant to commonly used antibiotics.

Study co-first author Dr. Sofya Podzniakova said: “Surprisingly, the Micrococcus luteus strain isolated was resistant to multiple drugs, including carbapenems, glycopeptides, ciprofloxacin, and trimethoprim-sulfamethoxazole.

“Our findings suggest that antimicrobial resistance could spread over long distances via this previously unrecognized route.”

The research team says the association of the aerosols with certain elements such as zinc sulfate and potassium, commonly used in fertilizers and pesticides, suggests an agricultural origin, consistent with intensively farmed croplands in northeast China.

They said that during the testing days, flight and ground samples were “very similar” in terms of microbial diversity, which can be explained by air descending from high altitudes to the ground.

The particle transport models corroborated both the possible transport of the particles from northeast China and the decline of tropospheric air masses to land in Japan.

Prof Rodó added: “Our findings uncover a rich and unprecedented diversity of microbes that are dispersed by wind currents thousands of kilometers away from their sources by intense tunnels of wind that form high in the troposphere.

“They represent a paradigm shift in our understanding of how human health can be affected by pathogens thriving in the environment, particularly in the air”.

He said that while the study doesn’t prove a causal link between the presence of known human pathogens in aerosols and health effects, it does emphasize the need to further explore the spread of different microbial pathogens over long distances.