The Rising Influence of Rising Affluence

[Biowatch]

Just how contagious is COVID-19?

https://www.popsci.com/story/health/how-diseases-spread/

Just how contagious is COVID-19? This chart puts it in perspective.
Everything epidemiology can tell us about the new coronavirus.
Matthew R. Francis
February 20, 2020

If somebody has a particular disease, the "R" number indicates how many people they are likely to infect.

If the R number is less than one, the infection will probably die out and disappear. If it's the flu, one person will probably pass it on to a few others.

Covid-19 is equivalent to the flu. Its rate of spread might even be lower if it wasn't a "new" virus.

Measles are the champions of infectious disease, with one sick child or adult able to infect of 18 others through casual contact.

Deadly serious

Another important number for understanding diseases is the "case fatality rate" or CFR: What percentage of people who have a disease die from it? On one extreme, we have rabies, which has a 99 percent fatality rate if untreated. On the other is the common cold, which has a relatively high R0 but is almost never fatal (the exceptions being mostly immunocompromised people). The seasonal flu has a low CFR, but enough people get it every year that the CDC estimates as many as 30,000 Americans may have died from it between October 2019 and February 2020.

Similarly, measles is extremely infectious, but rarely fatal (though its spooky effect on the immune system can make victims susceptible to other life-threatening diseases). Smallpox was less infectious with an R0 of 5 to 7, but its CFR of roughly 30 percent made it devastating. Measles, though less serious, has such a high infection rate that it needs a much larger vaccinated population for proper herd immunity; smallpox vaccines achieved herd immunity at much lower rates, and wiped the illness out entirely by 1980.

The CFR for an emerging disease like COVID-19 is remarkably hard to estimate accurately, simply because all the numbers involved are relatively small. A preliminary calculation from February 8, 2020 estimates CFR of about 1.4 percent—meaning out of 1,000 infected people, around 14 will die—but that’s based only on cases from outside China, since the data from that nation’s government has been unreliable. The numbers will likely shift over the next weeks and months, but the CFR for COVID-19 seems to be lower than for SARS and MERS. However, the high concentration of cases in one region of China is putting a huge stress on the healthcare infrastructure, which is a concern for any major epidemic.

Etc.