What caused my 8-month-old cat's sudden death after flu symptoms?

Hello and I am so sorry to hear about the passing of your kitty. It is so heart breaking to lose them. Without an autopsy, one can't be certain, but most often in a cat without any other clinical signs, it's usually a bad heart that will cause sudden death. One of the most most common heart diseases in cats is called Hypertrophic Cardiomyopathy. It often has no symptoms. It is often not detectable on a physical exam. Sometimes there will be fluid in the lungs from congestion in the lungs that can leak out after passing. I hope this helps to provide some closure and with time, I hope your heart heals. My condolences, Dr. Elizabeth

I am very sorry to hear that. This could be either due to an acute cardiac problem or respiratory one, but it is likely that the lungs filled up with fluid. A post-mortem examination would help to shed some light on the underlying cause of it.

He may have had an injury, been hit by a car or he had a congenital heart defect that caused a blood clot at the bifurcation of the aorta (that paralyses hind legs and hurts terribly). This can also cause a clot in the lungs which would cause breathing problems. Unfortunately most cats with these blood clots die within a short time. I am so sorry for your loss. This is very sad.

I am so very sorry that you lost your cats. Please accept my condolences for your loss. Without seeing them in person, I can't say what caused them to die, but it may have been something contagious. It could have been something like feline Panleukopenia, it's highly contagious. The other option is they all got into something toxic. Again, I'm sorry for your loss.

I'm so sorry you lost your cat so suddenly! An upper respiratory infection would not typically cause seizures. An upper respiratory infection can occasionally cause pneumonia or severe dehydration that could be life threatening but you would probably see other signs like trouble breathing or extreme lethargy. A heart murmur may or may not be related to underlying heart disease, but if there was heart disease present it could potentially lead to a seizure and sudden death. If he died recently you could consider taking him to your vet for a post mortem exam (autopsy) to try to determine what the cause may have been, but it can be difficult to know for certain.

There are three very common diseases that cats get that can cause his symptoms: diabetes, kidney failure and hyperthyroidism. If left untreated, all can cause death. I doubt a virus has much to do with it but of course it is possible. As for the vitamins, if they were made for cats that is not likely the cause. If it was not cat vitamins then it is possible he was overdosed. Not all vitamins are safe in large doses. I am sorry this happened and that he passed. In the future please get your cat examined by a veterinarian before the disease has progressed to this point. When they start losing weight that should be a good indicator that something is wrong especially if they are not eating and lethargic as well. Best wishes.

I'm so sorry this happened. Unfortunately there is no way for us to tell you why she died by looking at some photos. If you want to know for sure you will need to have a vet do an autopsy. If this way a young cat the two most common reasons for sudden death are trauma (like hit by a car) or poison ingestion.