By Karen Kelly
Photos by Bryan Gagnon
Carleton’s Hashmat Khan and Spanish co-author Miguel Casares (Universidad Publica de Navarra) develop a model to study COVID-19 containment measures.
Based on an approach that adapts the traditional Susceptible-Infected-Recovered (SIR) methodology for the study of epidemics and resembles Economic modelling, Hashmat Khan and his collaborator, Miguel Casares have demonstrated that isolation measures imposed by the Spanish government on March 14th have reduced the number of deaths by an estimated 95% in Spain, and lowered the maximum number of infected people who need daily hospitalization by 96% relative to the no-intervention scenario.
Their findings have important implications for self-isolation policies currently being implemented in Canada and other parts of the world. The model can be useful for health authorities and policy-makers, and also help in communicating the effects of the isolation measures to the public.
“Isolation measures work. They are very effective and you can put numbers to this,” says Khan, the Chair of Carleton’s Department of Economics. “We found proportionately greater effects as people reduced the number of daily interactions. That’s the best way to get the maximum effect.”
Khan and Casares compared the number of face-to-face interactions a person might have in a day combining it in the model with the probability of contagion and the ratio of infected population to determine the daily variation in newly infected people. The model also delivers daily values for the accumulated number of infected people cases, those who are hospitalized, and those who have died. The calibration started with 25 interactions a day with other people, then reduced it to 17, then eight face-to-face meetings.
“We found increasing returns where switching from 17 interactions to only eight had a much bigger effect,” explains Khan. Enforcing social distancing to lower face-to-face interactions from 25 to 3, Khan says the number of cases in Spain would be reduced to a level that the health system could handle.
“We have been hearing the notion of ‘flattening the curve’ of total cases to bring it within the capacity of the health care system. Our model generates this flattened bell-shaped pattern and provides an estimate in terms of number of people needing hospitalization and in how many days.” says Khan.
Responding to a Crisis
Typically, Khan and Casares collaborate on research in which they study the entry and exit of firms in the economy. They had never worked on anything related to the health care sector until Casares found himself in the centre of the COVID-19 outbreak in Spain.
“Everything is front and centre for him; with people in his social circle testing positive for it,” explains Khan. “So we started talking and thought, as economists, we build models and calibrate parameters (using actual data), then produce simulations to evaluate different policies. We could do the same to study the COVID-19 pandemic. It felt very urgent. By the time we completed the paper, Spain had already reached the second highest number of confirmed deaths (in Europe) after Italy,” notes Khan.
Khan and Casares will be sharing their findings with the policy and research institutions, as well as other researchers who are interested in applying the data from different countries. The main message is that both the timing and the intensity of isolation enforcement is critical for containing the virus spread and managing the capacity of the health care system.
The complete paper is available here.
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