So glad your ask is open! Is there any disease that could have someone coughing up blood and kill them within a few days? The timeframe of my story is short, so tuberculosis with its long incubation period wouldn't work. And the character isn't injured in any way, it's an attempt of biological warfare. Thanks!
Note: I initially missed theย โbiological warfareโ portion of this ask.ย
Hmmmm. So hemoptysis -- bloody sputum -- is a symptom of a few things.ย
One of those is arteriovenous malformation (AVM) of vasculature in the pulmonary system. If thatโs the cause, and the AVM is a symptom ob a bigger vascular problem, they could cause a fairly sudden death. I wouldnโt throw the book across the room if thatโs explained in the story.ย
The major causes of hemoptysis Iโm aware of are pulmonary edema -- blood flow backing up into the pulmonary vasculature until it floods the lungs -- and tuberculosis, which is legendary for it.ย
Perhaps your character had a heart attack, and they canโt clear their pulmonary vasculature, and they die fairly quickly of it. However, this would come with other unwanted side effects. A pulmonary artery aneurysm is possible but honestly fairly unlikely, because the pulmonary arteries are low-pressure systems.ย
One other cause: itโs really rare, but an aneurysm of the aorta can cause a fistula with the tracheobrochial tree (the physical space in which air passes), causing blood to enter the airway, and this could be rapidly fatal.ย
My issue in general with the bloody cough trope is that itโs... kind of misguided. Sure, itโs visually dramatic and so forth, but, if Iโm honest, basing a disease around one symptomย is backwards. Bloody cough is what you want. What you seem to needย is a rapidly fatal disease to give your character.ย
NOW THAT IโVE REREAD THE QUESTION LIKE A NOT-MORON, let me take this down the biowarfare tack. (Iโm leaving what Iโd already written because other people might have questions about bloody coughs.)ย
Biowarfare is interesting, and I honestly donโt know too much about it. Fortunately, in modern times it hasnโt been used much; chemwar is much more common and much easier to control and target.ย
Biowar weapons typically include difficult-to-kill viruses (such as ebola) or bacteria (like anthrax).ย
However, if youโre willing to make up a disease, you could realistically have a genetically engineered virus that attacks the lining of the lungs and airways, and they basically have bloody asthma to death. Youโd get a fever, wheezing, swelling in the airways, cough, then bloody cough, then death. Your evil bioweapon-maker characters could probably, in fact, modify a version of [RSV -- Respiratory Syncytial Virus] -- to suit their evil plans. (Theyโd have to modify it so that itโs extremely aggressive and also doesnโtย โlookโ like RSV to the immune system; adults are typically immune to RSV as we know it, but kids under 2 can have really bad cases of it. In fact, maybe this disease is special-built to target children...) eRSV (for Engineered) as a name, perhaps?ย
Sorry I donโt have anything realistic off-hand to give you as a bioweapon, but in all honesty, I feel a lot safer knowing that, too :)ย
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