Some Coronavirus Biology

The images below convey some information about how coronaviruses infect cells and reproduce. This is to try to demystify what is going on in an infected person and what some relevant biology considerations are.

Credit: By https://www.scientificanimations.com - https://www.scientificanimations.com/wiki-images/, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=86436446

Credit: By Crenim at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=26529404

Mutations tend to weaken viruses, not make them more virulent (lethal) & etc.

An explainer article that Nature published on Jan. 31, 2020 includes the following comments:

Is the virus here to stay? When a virus circulates continuously in a community, it is said to be endemic. The viruses that cause chicken pox and influenza are endemic in many countries, but outbreaks can be controlled through vaccination and keeping people at home when they are ill.

One big question is whether the coronavirus is also here to stay. If efforts to contain it fail, there’s a high chance that it will become endemic. As with influenza, this could mean that deaths occur every year as the virus circulates, until a vaccine is developed. If the virus can be spread by people who are infected but don’t have symptoms, it will be more difficult to control its spread, making it more likely that the virus will become endemic.

Is the virus likely to change? Kristian Andersen, an infectious-disease researcher at Scripps Research in La Jolla, California, is not concerned about the virus becoming more virulent. He says that viruses constantly mutate as part of their life cycle, but those mutations don’t typically make the virus more virulent or cause more serious disease. “I can’t think of any examples of this having happened with an outbreak pathogen,” he says.

In situations where a virus jumps from one animal host to another species — which is probably how the new coronavirus began to infect humans — there might be a selection pressure to improve survival in the new host, but that rarely, if ever, has any effect on human disease or the virus’s transmissibility, says Andersen. Most mutations are detrimental to the virus or have no effect, he says. A 2018 study2 of SARS in primate cells found that a mutation the virus sustained during the 2003 outbreak probably reduced its virulence.

How many people will it kill? The fatality rate for a virus — the proportion of infected people who die — is difficult to calculate in the middle of an outbreak because records on new cases and deaths are constantly being updated. With 213 deaths so far out of nearly 10,000 infections, the new coronavirus has a death rate of 2–3%. This is significantly lower than SARS, which killed around 10% of the people it infected. The known death rate for the new coronavirus is likely to decrease as mild and asymptomatic cases are identified, virologist Mark Harris at the University of Leeds, UK, told the Science Media Centre in London.

If the virus spreads throughout the world, the number of deaths could be substantial. The current death rate of 2–3% — while not as high as for SARS — is still quite high for an infectious disease, says Adam Kamradt-Scott, a global health-security specialist at the University of Sydney, Australia. The 1918 influenza outbreak, known as the Spanish flu, infected around half a billion people, one-third of the world’s population at the time, and killed more than 2.5% of those infected; some have estimated that as many as 50 million people died.

The China coronavirus probably won’t trigger such an apocalyptic scenario, because it isn’t typically infecting or killing young, healthy people, says Kamradt-Scott.