Infectious disease modelling, a scientist’s opinion
Interview with Professor Graham Medley, Professor of Infectious Disease Modelling and the Director of the Centre for the Mathematical Modelling of Infectious Diseases (CMMID) at the London School of Hygiene and Tropical Medicine, UK. He is also chair of the UK Scientific Pandemic Influenza Group on Modelling (SPI-M).
How does human behaviour shape disease transmission during an epidemic? What are the major determinants?
Generally infectious disease patterns in a population, the epidemiology, is determined by a combination of the biology of the pathogen, the environment, and the behaviour of the population. Of particular interest are the networks that behaviour creates which allow transmission from one person to create chains of transmission that connect the whole population. The structure and shape of these networks largely determine who is at greatest risk of infection and the scale and shape of the epidemic.
How is behaviour included in mathematical modelling of infectious diseases, and why is it important and useful?
Infectious disease dynamics are largely determined by the networks of transmission, so all the best models include data on human behaviour so that they contain realistic networks. Data can be basic demography (such as the number and size of households, number and size of schools), contact surveys (telling us how many contacts are typically made in different work settings) and time usage surveys. What we cannot yet do in models is to accurately predict human behaviour. Consequently, model output can only be in the form of “If 50% of people stop going to work then…”. Policy-makers then have to determine policies that achieve behaviour change they require.
What type or types of social behaviour drive disease transmission and/ or containment, what are the patterns we see, and how can they be measured?
For a directly transmitted, close contact infection such as COVID-19, the typical behaviour associated with transmission can be generically described as “sharing the same space”. The closer you are, the more likely transmission, and the longer two people are together the more likely the transmission. There is also a strong suggestion that environmental contamination places a role, so that people do not have to be in the same place at the same time, but that the virus can linger in places and infect the next visitor.