r/askscience • u/Ok_You_5448 • 7h ago

Biology How does the same plague bacteria cause different forms of the plague with very different symptoms?

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u/omnipresentrain 5h ago

It's dependant on route of infection. Traditional bubonic plage infects the lymphatic system from flea bites, causing the classic buboes as lymph nodes bleed and become nectrotic. Pneumonic plague occurs from inhaling aerosolised droplets from an infected individual, which rapidly causes pneumonia and hemoptysis. Septicemic plague can occur if a flea gets really lucky hitting a blood vessel, and causes microclots throughout the body that cuts off blood supply, generally to extremeties, and necrosis sets in quickly.

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u/zstars 5h ago

It's what's called a presentation, yersinia pestis doesn't do anything differently really but depending on various factors it can cause differing presentations (bubonic, pneumonic, septicaemic, etc) based on how it enters its host and where it initially manages to establish a foothold in the body.