It’s not the same cold, it has wandered around Brazil finding itself all summer and has mutated into a slightly different strain. Same symptoms, but different surface markers.

Now it’s back with a fake mustache and your immune system doesn’t recognize it anymore.

It's not the same cold. It's a slightly mutated version of last years' cold. This feels like a non-answer, but I have to ask, OP, if you understand natural selection, mutation, and microevolution?

The symptoms aren't caused by the same disease over and over. The symptoms are what your body does to fight the virus or bacteria. The cough and sneeze and sniffles are all intended to help your body expel the invader, the fever is an attempt to bake it to death or slow it's reproductive cycle so it can be fought.

Most of the diseases that affect the respiratory system will have very similar symptoms despite being different diseases.

That being said, the rhinovirus goes around, but much like how there's a new COVID Variant every few months, there's a new rhinovirus every few months. You won't catch Rhinovirus A if you e already had it but it's been a very successful virus and has a large family of variations and you might catch any that you haven't already had.

You get different mutated strains each year. You also get respiratory viruses of different types (flu, rhinovirus, coronoviruses, rsv, etc)

some people having the same illness seasonally can also be attributed to environmental or other seasonal habits (cold dry air , more indoor activities, interaction with asthma , copd etc) with seasonal temperature and humidity conditions making someone prone to respiratory infection

We aren't catching the same virus infection every year. Viruses trigger an immune response. An immune response triggers symptoms. Because we maintain the same immune system each year (we don't shed the old one to generate a replacement) we experience the same symptoms each year. Every person's immune system is slightly different which is why people will have different symptom severity. Keeping the same immune system each year is why a lot of vaccines are one time actions or only once every however many years (also because some viruses/infections don't mutate year to year) and our body has the data ready to fight off a return of that virus/infection.

By the time you experience symptoms, the infection has already been in your body and you're been potentially transmitting it to others. Symptoms are the body reacting to the activities of the immune system attempting to fight the infection. It's why people with low or no immune system won't experience fevers, diarrhoea, headaches, lethargy in the same way others with a healthy system do. They'll go straight to life threatening status or death.

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