Q&A: How particle-based simulators can aid contact tracing

Med-Tech Innovation News spoke to Aknur Karabay, research assistant at the Institute of Smart Systems and Artificial Intelligence at Nazarbayev University.

Karaby is one of five authors to a study that shows the joint use of mass testing and contact tracing of the infected people using a special mobile application can effectively suppress the spread of the virus and avoid strong restrictions and quarantine regimes being implemented – using a particle based COVID-19 simulator. 

The simulator presents people as small ‘particles’ on a 2D map with their position, velocity, infection state, availability of contact tracing application, and the results of COVID-19 testing. The contact tracing application informs individuals if they have been in contact with a ‘particle’ later found to be infected.

In their study, researchers used real data from the province of Lecco in the Lombardy region, which was the epicentre of the infection in Italy. In the course of modelling the spread of infection, the researchers found that the use of the two measures of contact tracing infected people and widespread population testing would significantly reduce infection and mortality rates.

On a 2D map, the model visually presents and divides people into infected and healthy ones by colour and shows their movement and the spread of disease. This, in turn, provides an idea of the volume of infected and healthy citizens on the 2D map, the number of people in who are infected or healthy, the speed of infection spread, and also helps in understanding the effectiveness of any measures taken.

What process went into the development of the particle-based simulator?

An SEIR (susceptible – exposed – infected – recovered) model has been used as a basis for the particle-based simulator.

Has this been used in other setting aside from the Lombardy region?

The simulator parameters can be adjusted based on the COVID-19 statistics of the region of interest. Accurate daily statistics are a prerequisite for a realistic and accurate analysis. To show full analysis, we limited the scope of this project to one specific location – Lecco Province, Italy. However, the simulator is completely customisable. 

How is the contract tracing technology used in this example different from the technology already being used? 

Basically, the idea of contact tracing is to keep track of contacts’ IDs and inform individuals in case one has been found to be infected. In this simulator, contact tracing used in combination with testing showed great effectiveness. It is important to note, testing parameters such as test sensitivity and specificity are considered. Contact tracing monitors the contacts of previously positively tested particles. If contacts of the positively tested particles are exposed, they are changed to true quarantined sub state, and if contacts are infected then they are changed to true isolated sub state. 

Contacts of the particles that are previously identified as false positive and changed to false isolated sub state, go to false quarantined. And after an exposure period, they become susceptible again.

The difference might be in the implementation and human factor. In the simulator, the transition between the states is done for all particles based on parameters you use, but in reality, the contact tracing has been integrated on a voluntary basis and does not guarantee 100% that people will follow suggestions. So, we have designed the potential outcome that could have been in case of usage of contact tracing in combination with testing. These results could be useful in illustrating the effectiveness of different policies and facilitate implementation. 

Can this be incorporated into existing and more well-known technologies used for tracing?

The main idea behind this project is the development of a tool that can simulate different scenarios and assess the effectiveness of certain policies in suppressing the pandemic at a particle level. The implementation of a contact tracing app is beyond the scope of this project. But yes, the classification and identification of particles based on the SEIR model we used could be integrated into current existing technologies.

How reliable is the particle-based technology?

To assess effectiveness and reliability of the particle-based technology, it should be implemented in real life. It should be able to provide adequate analysis, provided the accurate statistics are available and the simulations parameters – meaning contact tracing and testing – are accurately implemented in reality. Particle-based technology is very sensitive to parameters and proper fine-tuning should be done to provide reliable results. However, to validate our particle-based SEIR simulator, we have performed a validation analysis using official statistics from Lecco Province, Italy. 

What do you make of the current contact tracing capabilities already available?

There are a number of contact tracing applications that have been used in different countries that use different technology and they all have quite good potential and effectiveness. The key issue to consider here is privacy, along with implementation. There is some technology that uses Bluetooth technology that does not use personal data such as geolocation. However, human factor and problems with reaching people to inform them of their infection status might not work for all cases efficiently. So, practical aspects need to be properly developed in order to provide effective usage of existing contact tracing technology capabilities.

Anything else to add? Any future developments?

The combination of contact tracing and testing shows good effectiveness in suppressing the epidemic spread based on our simulations. For practical implementation of contact tracing, the environment might be an important aspect to consider further, as indoor and outdoor spread is different.

The authors involved in the study are Askat Kurdeuov, Aknur Karabay, Daulet Baimukhashev, Bauyrzhan Ibragimov and Huseyin Atakan Varol.