A cold or not a cold? What is a cold?

In humans, contagious viral upper respiratory tract infections are classed in two broad categories: the cold and the flu. 

The flu or Influenza spreads around the world in yearly outbreaks, resulting in about three to five million cases of severe illness and about 290,000 to 650,000 deaths. About 20% of unvaccinated children and 10% of unvaccinated adults are infected each year.^[14] In the northern and southern parts of the world, outbreaks occur mainly in the winter, while around the equator, outbreaks may occur at any time of the year.^[1] Death occurs mostly in high risk groups—the young, the old, and those with other health problems.

Each virus type is different. You don't get the same virus twice because of antibodies. At times, the flu can be deadly. The example most widely known is the Spanish Flu from 1918, which killed more people than the first world war. 

For Flu, we have vaccines -- each year a different one, as the viruses change. We also have some dedicated antiviral drugs like Tamiflu, etc. 

Common Colds are cased by hundreds of different viruses of several different types such as rhinoviruses, coronaviruses, adenoviruses,  human respiratory syncytial virus (HSV) and others. Colds are usually mild, but, on occasions, they can cause complications. The most common complication is a lower respiratory tract infection like bronchitis, bronchiolitis and pneumonia. Some cold viruses also play a surprising and interesting role in obesity.  There is no specific treatment and no vaccine. Therapy is usually just supportive -- keep the patient alive while the immune system solves the problem.

HSV causes pneumonia in children. It used to be a significant contributor to childhood mortality in the past. In western countries, high risk children are periodically injected with an antibody against HSV like palivizumab.

Adenoviruses cause about 5% of colds and may play a role in causing obesity after the cold has healed [2,3, 4]. 

Coronaviruses used to cause 10-15% of colds. It will be more this year, as COVID-19 joined the party and will probably infect a significant portion of the world population. 

There are 7 coronaviruses that infect humans:

1. Human coronavirus OC43 (HCoV-OC43)

2. Human coronavirus HKU1

3. Human coronavirus NL63 (HCoV-NL63, New Haven coronavirus)

4. Human coronavirus 229E (HCoV-229E)

– and three with symptoms that are potentially severe:

5. Middle East respiratory syndrome-related coronavirus (MERS-CoV), previously known as novel coronavirus 2012 and HCoV-EMC

6. Severe acute respiratory syndrome coronavirus (SARS-CoV or "SARS-classic")

7. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), previously known as 2019-nCoV or "novel coronavirus 2019". It is the cause of the  current COVID-19 pandemic. The virus is classed as potentially severe, albeit it is now clear that it is a lot less deadly than the other two. 

I thus rest my case. COVID-19 is a cold, just like the Spanish Flu was a flu. 

I have shown COVID-19 classifies as a cold, but this does not mean it's not deadly. However, if the mortality rate is of the order of 0.2% as I guess/estimate, it is not as bad as WHO fears. More tests have to be done to ascertain the mortality rate. Testing symptomatic people gives an apparent mortality that is much higher than the true mortality where all the asymptomatic cases are included.