Many felt ready for the crisis period of the Pandemic to be over when scientists predicted that Covid-19 could be entering an endemic phase. The idea that coronaviruses might be just another cold felt good. The emergence of the Omicron variant just weeks before Christmas shows that this is not guaranteed to be a smooth transition.
Will the virus become milder?
A recurring suggestion is that pathogens evolve to be more transmissible and less virulent, bringing the virus and host to a state of benign coexistence. Some wondered if Omicron will be milder if it is spreading so quickly. Experts say this expectation is not scientific. Prof Alan McNally, director of the Institute of Microbiology and Infection at the University of Birmingham, said that this has been one of the most baffling misinformation myths peddled during the Pandemic. There is no evidence of a human virus evolving to be less virulence.
If a pathogen kills its host, or makes them too sick to leave the house, then it gives itself a worse chance of propagating. There would be a pressure on milder strains by the logic of survival of the fittest. In the real world, the dynamic is more complex.
Brian Ferguson is an immunologist at the University of Cambridge. You can pick out examples of things going one way or the other.
There is an obvious hole in the argument that the severity of illness has little influence on the spread of the coronaviruses, because transmission usually occurs before symptoms start or during the earliest stage of symptoms.
The impact of Covid may become less each year as immunity builds up.
Will it get more transmissible?
Probably. Prof Kit Yates, a senior lecturer in mathematics at the University of Bath, said that strains that transmit more easily will have an advantage over strains that are less transmissible. The original variant had a basic R number of 3, followed by Alpha with an R0 of 4-5 and Delta with an R0 of 6.
