Dear Reader:

Summary and some editing of my posts in my previous thread on Covid-19:

The official name of the disease behind this pandemic is COVID-19, an acronym for Coronavirus Disease- 2019 (I personally type “Covid-19”). The official name of the virus causing the disease is SARS-Cov-2, an acronym for Severe Acute Respiratory Disease Corona Virus 2.

As the name suggests, it is a Severe and Acute respiratory disease.

There are currently 7 known coronaviruses that infect humans, all of them attack the respiratory system. A few are mild, others are severe. They differ in how contagious they are (their basic reproductive number, R0 is different; Ro means how many healthy individuals get infected by one infected individual, an Ro of 2 means that each infected individual infects two others) and how deadly they are (mortality rate/ fatality rate).

The first two coronaviruses that attack humans  were discovered in the 1960s, and both cause the common cold (in combination with other viruses). A third coronavirus was discovered in 2003 in China, and it was responsible for the first of the two SARS outbreaks 2002-2003, 8,422 cases spread to 17 countries. The second outbreak developed to our current pandemic, over 16 million cases today, July 25). SARS-Cov, the coronavirus responsible for the first SARS outbreak was less contagious, and more deadly (11% fatality rate). The current SARS-Cov-2 is way more contagious, and therefore, over time, way more deadly.

MERS-Cov is the virus behind the Middle East Respiratory Syndrome (MERS)  outbreak of 2012 in the middle east, having spread to South Korea and a bit elsewhere, total under 2,000 cases. MERS-Cov was more deadly than SARS-Cov and way more deadly than SARS-Cov-2 (36% fatality rate). But it was way less contagious than our current SARS-Cov-2, and therefore, the latter, over time, is more deadly.

Smallpox (Ro= 3.5-6), Mumps (Ro= 4-7), Rubella (Ro= 5-7), Polio (Ro= 5-7) and Measles (Ro 12-18) are all  more contagious than SARS-Cov-2 (Ro= 1.4-3.9). The reason for the current virus being as successful as it is (that is, being as destructive to us humans, as it is), is that it got out of hand, meaning, too many people in different areas in the world were infected: a lot of people infected with a virus of a lower R0, bring about many more infected individuals, than a small number of people infected with a virus with a higher Ro.

Another factor that influences how infectious a virus is, is the method by which it gets transferred from one individual to the next. Viruses that get transferred by body having sexual intercourse are less contagious than viruses that get transferred by breathing/ through the air (we can avoid sexual intercourse, but we can’t avoid breathing). Of the viruses that are transferred through the air, those that transfer in bigger droplets of liquid are less contagious than those transferred in very small droplets aka airborne viruses, because bigger droplets respond to gravity and fall down way sooner than very small droplets that remain suspended in the air for a long, long time.

Regarding the viral diseases I mentioned above, those with high R0s-  there are effective vaccines for all thee, but none yet for SARS-Cov-2.

-Summary and editing to continue later.

anita

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