this link contains a gigantic chart comparing the coronavirus with other pandemics in history
Wonderful perspective Gunter!
We should keep in mind that the world population today is almost 8,000,000,000 which is many times greater than for most of those epidemics.
If we used % of the population, the coronavirus epidemic would really look tiny....so far.
Knowing that such papers would come out during this outbreak, Grubaugh published a commentary in the journal Nature Microbiology on Feb. 18. with the title "We shouldn't worry when a virus mutates during disease outbreaks."
The word mutation "naturally conjures fears of unexpected and freakish changes," he wrote. "In reality, mutations are a natural part of the virus life cycle and rarely impact outbreaks dramatically." RNA viruses, or those that have RNA as their main genetic material instead of DNA, including SARS-CoV-2, mutate constantly and do not have the mechanisms to fix these "mistakes," as human cells do, for example.
But most of these mutations negatively affect the virus. If mutations are not beneficial to the virus, they are typically eliminated through natural selection, the mechanism of evolution whereby organisms better adapted to their environment tend to survive. Other mutations survive and get embedded into the "average" genome of a virus.
Typically, multiple genes code for traits such as a virus's severity or ability to transmit to other people, Grubaugh wrote. So, for a virus to become more severe or transmit more easily, multiple genes would have to mutate. Despite high rates of mutation among viruses in general, it's unusual to find viruses that change their mode of transmission between humans over such short time scales, he wrote.
Researchers say undiagnosed cases fueled the rapid spread in China.
A new study estimates 86 percent of COVID-19 infections in China went undiagnosed before the country enforced a travel ban in late January, leading to the rapid spread of the virus.
Researchers behind the study published in Science Monday used mathematical models to simulate the outbreak and calculated the contagiousness of people who were reported to have the COVID-19 virus and the estimated number of undocumented cases.
The study found that undocumented cases transmitted the virus about half as often as documented cases, but there were significantly more undocumented cases. Researchers said those who were not diagnosed were the source of about 8 out of every 10 infected cases in China before Jan. 23.
“It’s the undocumented infections which are driving the spread of the oubtreak,” Columbia University’s Jeffrey Shaman, a co-author of the study, said according to GeekWire.
Those who are not diagnosed often experience mild symptoms or none at all, leading these patients to “expose a far greater portion of the population to the virus than would otherwise occur,” the study said.
Researchers estimate that if the virus among undiagnosed people had not spread, the amount of cases may have been reduced by 66 percent in Wuhan, the city at the epicenter of the outbreak, and by 79 percent across China.
“More active testing procedures would catch more cases,” Shaman said. “How that would be implemented is something that we can debate for quite some time. And obviously this all has to be done under the backdrop of the logistics and costs of implementing lots more tests.”