Sars CoV-2 is the 2nd Sars corona virus which causes Covid 19 and for some. Long Covid. SARS was the first which had a much higher death rate (over 10%) and only occured in China. MERS was another corona virus very close to SARS and Sars CoV-2 which only occured in the Middle East. Together, these are like triplets of the Corona Virus Family. MERS also had a high desth rate over 10%.

The names follow this scientific method: a pathogen (a virus or bacteria or fungus most of the time) causes a "disease" or syndrome. In this case, Sars CoV-2, Severe Acute Respiratory Syndrome Corona Virus-2, causes the named disease "COVID-19".

One is infected by the virus and the symptoms caused are the diease which is called COVID-19. The after effects of the damage from the virus to the body are what causes Long Covid.

You should take your dad to the ER. He may need steriods to reduce inflamation in his lungs, antibiotics such as a ZPack to prevent pneumonia, and fluids to prevent dehydration which is a major issue with older people.