The investigators will work the phones and connect the dots of who could be spreading coronavirus.
Belgium will hire 2,000 call centre staff tasked with investigating suspected cases of coronavirus.
The staff members will speak to people who have the virus, figure out who they have been in contact with, and then notify anyone they think may have contracted it.
"For each newly-infected person, the investigator would contact them by asking who they have been in contact with for the past 14 days," explained Gilles Vanden Burre, a Belgian MP.
"After that, the call centre person will call these people to say: you have been in contact with someone who tested positive for Covid-19 today, so we recommend a whole series of things. However, of course, you never give the name of the person."
The initiatives come as European states prepare to make the transition out of lockdown without a spike in cases as citizens return to work, schools and public spaces.
"With the strategy of leaving lockdown, reopening businesses, we hope to see our families, our friends very quickly, in small groups," says Burre.
"It is essential to be able to track the evolution of the disease in detail, because otherwise there is a risk of having a new peak in a few months and containment measures will have to be taken again, which no one wants."
France, where the lockdown is due to end on May 11, has launched a national phone line staffed by so-called "digital assistants" who will help check whether callers have symptoms of COVID-19.
Callers to the free AlloCovid service will be put through to one of 1,000 "intelligent virtual agents" which will listen to symptoms and assess whether they are likely to have been infected.
Other countries - including China and Israel - have launched mobile phone tracing apps that allow the authorities to track where people with coronavirus have been and who they have contacted.
But in Europe, concerns have been raised about civil liberties and data protection. As such, Belgium's call centre staff would not reveal the names of COVID-19 cases to others.