Coronavirus is on everyone’s mind at present, including mine at about half past 5 this morning, when my mobile phone made an alert sound, but I could not find any message. There was a quick flash of what looked like the NHS Covid-19 app, which I have recently installed. In the way that the brain does in mind-wandering mode (as described in The Organized Mind) a connection between the Covid-19 Pandemic and Catastrophe Theory came into my mind. I have not done any of the mathematical modelling needed to take demonstrate that Covid-19 is a Catastrophe in the mathematical sense, but, as it feels like one, wanted to explore some of the implications.
Catastrophe theory is used to model systems which can be in one of two semi stable states, and switch rapidly from one to another. Classic examples are the financial markets, which can switch from being a Bull Market to a Bear Market or house price booms and busts.
Feedback is an essential part of these systems. In the case of the financial markets the controlling factor is investor confidence. If people are confident about the future they will buy houses, or shares, the price will go up, others will see this rise and also want to buy shares, or houses. In an infectious disease case the controlling factor is the rate at which the disease is spreading.
If every person who has Covid-19 passes it on to more than one person then it will spread, becoming a epidemic, with a potential end point of being endemic, that is to say in a widespread stable state, like flu. In the case of Covid-19 there will be medical penalty to pay if this happens. Medical resources need to be spent dealing with patient treatment, both for acute patients in Intensive Care Units and for chronic cases – the Long Covid cases. This is one possible stable state.
On the other hand if Covid-19 can be brought under control, then there is an opportunity for it to eliminated at a national level, as may be feasible for China and New Zealand. Medical resources are focussed on rapid detection of cases and preventing transmission. This is another possible stable state, and has been reached worldwide for some diseases, such as smallpox. This requires good data, and a rational plan of action, an example of the situations I describe in ‘The reasoned feedback loop‘.
If the world becomes divided between countries where Covid-19 is endemic and those where it is eliminated then this has major implications for tourism and international travel. Will tourists from a Covid-free country wish to visit one where there is a good chance they will catch a disease which may make them seriously ill. Even with the development of a vaccine it will be harder to avoid catching Covid-19 than, for example Typhoid or Yellow Fever due to the differences in the way these diseases are transmitted.
If you travel by train from London Marylebone to Oxford the announcements are in Chinese as well as English, as Bicester Village, which is served by that route, was very popular with Chinese tourists. If Britain becomes one of the countries where Covid-19 is widespread, and China becomes one where it is rare then I wonder if those tourists will return.