This question was recently brought into focus by the publication of a paper speculating that India’s Covid-19 epidemic would end in Septemb...
This question was recently brought into focus by the publication of a paper speculating that India’s Covid-19 epidemic would end in September. While this outcome seems highly unlikely, the question of how and when India’s Covid-19 epidemic might end is a valid one.
The good news is that elimination can occur. New Zealand appears to have achieved elimination and other countries, such as Vietnam, South Korea and Australia may soon follow suit. But in many countries, including India, Covid-19 seems to be the unwanted guest who just will not leave.
The goal here is to try, with the help of modelling, to unpack the processes by which Covid-19 epidemics can be controlled – even ended. First, it is helpful to think about what Covid-19 epidemics do not do, and that is best summarised in pictures we see often which look something like this.
The symmetric rise and fall of an epidemic in such pictures is encoded in an empirical principle known as “Farr’s law”, postulated after studying data from smallpox outbreaks. But real Covid-19 data stands in sharp contrast to the neat symmetry of Farr’s law. Whether countries have been fairly successful in controlling their outbreaks (for example Germany and Denmark), or less so (for example the UK and the US),...
