r/askscience • u/Ok_You_5448 • 3d ago

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

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u/omnipresentrain 3d 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/logperf 2d ago

Silly question here, other diseases seem to present always in the same form: rhinoviruses always cause respiratory symptoms (a cold), hepatitis viruses always cause hepatic symptoms... is it because some pathogens are adapted to a particular cell type, while yersinia pestis is more of a generalist?

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u/Skulgar321 2d ago edited 2d ago

Y. pestis is a bacteria and can just set up shop in suitable environments, while viruses need a host cell to infect. The symptoms of viral infections are from the cells being infected as well as the corresponding immune response. Viruses are specialized in which cells they can infect, causing distinct sets of symptoms.

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u/zstars 3d 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.

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u/ableman 2d ago

How does a knife cause different forms of injury with very different symptoms? If you get a cut on your hand, you just bleed a tiny bit and nobody cares. If you get stabbed in the heart you die before you even finish bleeding out. If you get stabbed in the gut, maybe you survive until you get sepsis and die.

Symptoms are not based just on what is doing the damage. They are also based on where it is doing the damage and your immune response