Smokers gave a home to bacteria that now sicken people with cystic fibrosis

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Smoking can really clog up the lungs, even for people who've never been near a cigarette. Turns out that smoking habits from the early 1900s are still inflicting damage-not on tobacco users or their families, but on people with cystic fibrosis.

Cystic fibrosis (CF) is a hereditary condition that makes afflicted people's mucus thick and sticky. Their lungs become breeding grounds for bacteria that healthy people's immune systems easily defeat. People with CF often take antibiotics to prevent lung infections, but antibiotics don't kill everything. A bacterium called Mycobacterium abscessus (M. abscessus) is resistant to many common drugs, and it has become a plague in the CF community over the last couple of decades.

A few years ago, scientists began investigating how the plague originated. By analyzing M. abscessus genomes collected from people around the world, the researchers traced the bacterium's spread over the last century. They found that decades before the 1950s-before medical advances let people with CF survive past infancy-M. abscessus was already spreading around the globe, and an old public health enemy was to blame. Smokers' lungs created a reservoir where the pathogen could live and reproduce, a reservoir that quickly spilled over when people with cystic fibrosis began living into adulthood.

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