The virus belongs to the family Coronaviridae, which are RNA viruses with relatively large genomes. The SARS-Cov-2 virus has 29,891 nucleotides. That’s twice as large as an influenza virus genome. What’s more, the coronavirus family undergoes relatively rapid genetic “recombination” in nature, including mutations that enable the virus to adapt to new hosts and environmental niches. In this case, the genetic blueprint probably came initially from nature, perhaps from bats.
A cousin of this virus is SARS-Cov-1, which caused an epidemic of severe acute respiratory syndrome in 2002 and 2003 that began in China and ended with 774 deaths in 17 countries. The genetic material in the current virus is an 82 percent match for the earlier SARS virus. Another type of coronavirus found in bats is an 89 percent match for the current virus. Not every mutation changes behavior, but even a minuscule change in the genetic makeup may have given the current virus the characteristics that allowed it to survive, thrive and unleash the current pandemic.
The virus is an opportunistic parasite with a singular mission: dock on the surface of a cell using its exterior spikes, then penetrate and hijack the cell to replicate, creating millions more copies of the virus with its genetic code. In the coronavirus family, some strains cause only minor illness such as common colds and, in others, disease more serious than covid-19. Two related viruses, the one causing SARS and the one causing Middle East respiratory syndrome, or MERS, are more lethal, but the current virus is more transmissible, lodging in the upper respiratory tract, the nose and throat, where it is easily expelled by a cough. Another characteristic accelerating transmission is that an infected person can be contagious several days before any symptoms show up. A cough or sneeze expels virus particles in aerosol droplets, which can remain in the air for hours. Also, there’s evidence of survival on plastic and stainless steel for up to 72 hours. The current virus leads to acute respiratory distress in some people, filling lungs with fluid, constricting their ability to breathe, especially those who are already suffering another malady.
The virus is not invincible. It is sensitive to ultraviolet rays and heat, and hand-washing works. Biomedical researchers are racing to discover therapies to stop it from infecting people, perhaps with an antiviral drug that would disable those exterior spikes, or a vaccine that would instruct the human immune system to attack it. Hopefully, we can bend the curve slightly in favor of people and stop the pandemic. But even if science triumphs this time, genetic recombination and mutation will go on.