The Covid-19 pandemic has led to intense scrutiny of the role of modelling as a tool for guiding public health policy. From the outset of the pandmic models were used to produce numerical predictions of likely outcomes, measured in terms of hoospital occupancy and disease induced mortality. The initial models were produced through adapting models designed to predict the dynamics of epidemics such as flu. Emerging data led to more empirical approaches to prediction being adopted.(Birge, Candogan, and Feng 2020; Gomes et al. 2020; Levitt, Scaiewicz, and Zonta 2020; Lipton and López de Prado 2020; Lourenço et al. 2020)
There has been relatively little discussion of the role of models as frameworks for thought regarding underlying dynamics.
The SIR model of Kendrick and McKormak has been used to model epidemics and even pandemics. However the model only provides a framework for thought regarding the dynamics of the spread of infection over a population with complex spaially and socially determined connections. The SIR model is best suited to modelling outbreaks, rather than epidemics. Epidemic and even pandemic dynamics may approximate to the SIR if many synchronous outbreaks are considered as additive in effects. However this is simply a coincidental outcome. It is difficult to
Birge, John R., Ozan Candogan, and Yiding Feng. 2020. “Controlling Epidemic Spread: Reducing Economic Losses with Targeted Closures.” SSRN Electronic Journal. doi:10.2139/ssrn.3590621.
Gomes, M Gabriela M, Rodrigo M Corder, Jessica G King, Kate E Langwig, Caetano Souto-Maior, Jorge Carneiro, Guilherme Goncalves, Carlos Penha-Goncalves, Marcelo U Ferreira, and Ricardo Aguas. 2020. “Individual variation in susceptibility or exposure to SARS-CoV-2 lowers the herd immunity threshold.” medRxiv : The Preprint Server for Health Sciences, 1–10. doi:10.1101/2020.04.27.20081893.
Levitt, Michael, Andrea Scaiewicz, and Francesco Zonta. 2020. “Predicting the Trajectory of Any COVID19 Epidemic From the Best Straight Line.” medRxiv : The Preprint Server for Health Sciences, June, 2020.06.26.20140814. doi:10.1101/2020.06.26.20140814.
Lipton, Alex, and Marcos López de Prado. 2020. “Mitigation Strategies for COVID-19: Lessons from the K-SEIR Model.” SSRN Electronic Journal, 1–45. doi:10.2139/ssrn.3623544.
Lourenço, José, Francesco Pinotti, Craig Thompson, and Sunetra Gupta. 2020. “The impact of host resistance on cumulative mortality and the threshold of herd immunity for SARS-CoV-2.” medRxiv, July, 2020.07.15.20154294. doi:10.1101/2020.07.15.20154294.