Researchers from KU Leuven propose a different approach to contact tracing. “More than 70 percent of people do not transmit the virus.”
If the catering industry is allowed to reopen from 1 May, the contact tracing must be done differently. This is what Klaas Nelissen and Joren Raymenants say, who designed the local contact study of KU Leuven and are responsible for approximately 50,000 students. Their work shows how important backward contact tracing, or source tracing, is.
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If the catering industry is allowed to reopen from 1 May, the contact tracing must be done differently. This is what Klaas Nelissen and Joren Raymenants say, who designed the local contact study of KU Leuven and are responsible for approximately 50,000 students. Their work shows how important backward contact tracing, or source tracing, is. Currently, the Flemish contact investigation works with forward contact tracing: confirmed covid-19 patients are asked to share their close contacts with the contact investigators. These high-risk contacts are then called. “The government is very efficient in identifying and quarantining those people,” say Nelissen and Raymenants. But that is not enough. The Flemish contact investigation, carried out by a collaboration of health insurance funds and call centers, does not go back far enough in time to investigate where the infection has contracted. To date, contact researchers mainly ask where people think they are infected, but Nelissen and Raymenants take a different approach. ‘More than 70 percent of people do not transmit the virus. If a person is infected, it is very likely that the infection was contracted at some sort of meeting, ‘they say. They plainly state that their method of backward contact tracing has already identified infected individuals who had slipped through the net in regular contact research. “We therefore need to shift the focus from individuals to events,” say the researchers. They almost always reduce a source of contamination to a situation where there are the ‘three Cs’: poorly ventilated spaces (closed spaces) with many people (crowded places) who do not keep their distance (close contact). The registration of data therefore remains essential. This is all the more true for the coming period, when more events will gradually take place. Was our data not already registered at events? In the summer of 2020, we did not enter a cafe or restaurant without providing our contact details. The obligation was intended to facilitate the contact investigation when a customer would test positive, and thus make the catering visit safer. But the data turned out to be gathering dust. Between September and mid-October, the central Flemish contact investigation requested barely 25 lists, but a turnaround at the Flemish level is not immediately possible. Flemish Minister of Welfare Wouter Beke (CD&V) says that the intensive source tracing that Nelissen and Raymenants use is only possible with a maximum of ten infections per 100,000 inhabitants, for a period of two weeks. By way of comparison: in Flanders that number fluctuated around 330 last week. The researchers admit that source tracing is time-consuming. Their work is facilitated by the limited target group: students in one city, who often infect each other at kot parties. In any case, their project arouses interest. Virologist Emmanuel André (KU Leuven) explained the results of the research to Corona Commissioner Pedro Facon, and colleagues from Louvain-la-Neuve have already contacted. Ideas have also been exchanged with student cities of Ghent, Antwerp and Brussels. This gives the students hope for more possibilities.
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