It’s the Corona Virus, so what does the letter D stand for in COVID19? ~

  That’s either inaptly named or redundant. Inapt because not every virus is a disease and/or it’s either a virus or a disease, but not both. Redundant because if a virus is a disease, then it makes as much sense as saying PIN number, or ATM machine.
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Not all viruses cause a disease and not all diseases are caused by viruses. Diseases can be caused by a variety of things (virus, bacteria, lifestyle, injury, heredity). 

Pneumonia is a disease that can be caused by bacteria, virus, fungus. 

The word "disease" is basically something that's not well or is malfunctioning, and doesn't in itself refer to a cause (such as virus). 

Corona Virus Disease that was identified in 2019. Why they changed it from 2019nCoV (2019 novel corona virus), I don't know. Probably too many letters and numbers. 

They changed because they learned it is a form of SARS. So not a new/novel virus.   The virus name is SARS-CoV-2.   Covid-19 is the disease caused by SARS-2. 

A virus can exist without being a disease. A disease can be caused by something other than a virus. In this case, the Corona virus leads to a disease. 

Thanks!
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Thanks!
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