Sydney in lockdown, page-31

Not true.

https://theconversation.com/will-coronavirus-really-evolve-to-become-less-deadly-153817

"A challenge to the law of declining virulence
At around the same time, a talented young Australian mathematician named Robert May came across the work of his compatriot Charles Birch, an eminent ecologist working on the regulation of animal populations. Together with epidemiologist Roy Anderson, May went on to pioneer the application of mathematical modelling to the ecology and evolution of infectious disease. By the late 1970s, May and Anderson had developed the “trade-off” model for the evolution of virulence – the first conceptual framework in 100 years to challenge the Smith’s general law of declining virulence.

The trade-off model recognises that pathogen virulence will not necessarily limit the ease by which a pathogen can transmit from one host to another. It might even enhance it. Without the assumed evolutionary cost to virulence, there is no reason to believe that disease severity will decrease over time. Instead, May and Anderson proposed that the optimal level of virulence for any given pathogen will be determined by a range of factors, such as the availability of susceptible hosts, and the length of time between infection and symptom onset.

This last factor is a key aspect of the epidemiology of SARS-CoV-2. The long time period between infection and death (if it occurs) means that SARS-CoV-2 has a significant window in which to replicate and spread, long before it kills its current host.

The trade-off model is now widely accepted. It emphasises that each host-pathogen combination must be considered individually. There is no general evolutionary law for predicting how these relationships will pan out, and certainly no justification for evoking the inevitability of decreased virulence.

There is little or no direct evidence that virulence decreases over time. While newly emerged pathogens, such as HIV and Mers, are often highly virulent, the converse is not true. There are plenty of ancient diseases, such as tuberculosis and gonorrhoea, that are probably just as virulent today as they ever were.A change in conditions can also drive the trend in the other direction. Dengue fever has afflicted humans since at least the 18th century, but an increasingly large and mobile human population is thought to have driven a marked increase in virulence over the last 50 years or so. Even the seminal case of the rabbit-killing myxoma virus is uncertain. There was little subsequent decline in virulence after Fenner’s early reports, and it may even have risen slightly."