petri dishes
© Fabian Bimmer / Reuters
Milliarder af virus falder ned fra himlen hver dag. Det fortæller ny forskning, som kan give en forklaring på, hvorfor genetisk identiske virus ofte findes i meget forskellige omgivelser rundt om i verden.

Et internationalt hold af forskere har for første gang optalt antallet af virus, som fra Jordens overflade hver dag hvirvles op i den frie troposfære - det nederste lag af atmosfæren, hvor næsten alt vejr finder sted.

Studiet, som er offentliggjort i International Society for Microbial Ecology Journal, beskriver registreringen af hundreder af millioner af virus og bakterier, som regner ned fra himlen hver dag.

"Hver dag afsættes mere end 800 millioner virus per kvadratmeter af det planetære grænselag [Eng: planetary boundary layer] Det er 25 virus for hver person i Kanada" siger medforfatter og virolog ved University of British Columbia, Curtis Suttle i en udtalelse.


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Bacteria and viruses are swept up into the atmosphere in small particles from soil-dust and sea spray. The pathogens can be carried thousands of kilometers overhead before being dropped back onto the Earth's surface. The phenomenon helps explain how the same virus ends up in notably different environments.


"Bacteria and viruses are typically deposited back to Earth via rain events and Saharan dust intrusions. However, the rain was less efficient removing viruses from the atmosphere," study co-author and microbial ecologist Isabel Reche from the University of Granada said.

Scientists conclude while the deposits of bacteria and viruses from the atmosphere may have effects on the structure and function of recipient ecosystems, it's not necessarily terrible news, as the deposits could help ecosystems adapt more quickly to environment changes.