Modelling an epidemic

Thinking

All political measures are based on modelling the Covid-19 pandemic. But there is an important precondition for modelling near to reality – to understand the biology of the virus:

“Better understanding of who is responsible for transmission and when during the disease progression is a really important piece of the jigsaw and we still don’t have any real insight.”

“I keep hearing about significant asymptomatic infection, for example the US Navy personnel, but still have no real idea as to how important they might be with respect to spread.”

Professor Jonathan Ball, virologist at Nottingham University [1]

Experimenting with a model

We like to show the effect with help of a simplified Epidemic Calculator[2], implementing a classical infectious disease model.

One of the key factors for any epidemic is the incubation period – that is the time between first contact with a pathogen and the first symptoms. For SARS-CoV-2 the WHO estimates the incubation period still between 1 and 14 days, usually avering 5 days [3]. If we ran SARS-CoV-2 through the simulated model, what would be the impact of varying the incubation period, while keeping all other variables constant?

The graphics below show the effect. Out of an assumed population of 7 million people, and an incubation period of just 1 day, 1.5 million people would be affected at the peak, whereas, with an incubation period of 14 days, only 800 people would be affected, with the peak being about 40 days later.

Incubation period 1 day:

Epidemic model with incubation period 1 day

Incubation period 5 days:

Epidemic model incubation period 5 days

Incubation period 14 days:

Epidemic model incubation period 14 days

We understand that already slight modifications of a key factor can have tremendous effects.

Therefore, our research project will focus on establishing key factors such as susceptibility, incubation period, cross-immunity and recovery, in order for most effective handling of another outbreak wave, or a similar epidemic, to be assessed.


References:

[1] The Guardian 2020-04-21: Boy with Covid-19 did not transmit disease to more than 170 contacts
https://www.theguardian.com/world/2020/apr/21/boy-with-covid-19-did-not-transmit-disease-to-more-than-170-contacts

[2] Epidemic Calculator
http://gabgoh.github.io/COVID/index.html

[3] WHO Q&A on coronaviruses
https://www.who.int/news-room/q-a-detail/q-a-coronaviruses