A few weeks ago there were none. Three weeks ago, with an entirely inadequate search strategy, ten cases were found. Last Saturday there were 43! With three inaccurate data points, there is enough information to fit an exponential curve: the prevalence is doubling every seven days. Armchair epidemiologists should start worrying that by Christmas there will be 10¹² preprints relating COVID-19 to weather and climate unless an antidote is found.

Fortunately, a first version of an antidote to one form of the preprint plague that is sweeping the planet known as the SDM (apparently this not an acronym for Simplistic and Dangerous Model). A second version is due to be published soon.

So why are SDMs such a bad tool for trying to model the spread of COVID-19?

1) The system is not at equilibrium

The first case of what has become known as COVID-19 was reported on