\laptop\sequeris\virulance.txt The less virulant strain has a larger Ro and produces some resiliance or limited immunity to the more virulant strain. https://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2008.01658.x Virulance evolution and the trade-off hypothesis: history, current state of affairs and the future https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5115872/ A transmission-virulence evolutionary trade-off explains attenuation https://evolution.berkeley.edu/evolibrary/news/071201_adenovirus sway pathogen evolution towards less virulent strains favor the evolution of less virulent strains of the virus