On Wednesday evening, the health minister, Paulette Lenert (LSAP), said that 33 clusters were identified during the week of 13 to 19 July. Roughly a third were identified at schools.

A cluster is flagged when at least three people have been identified as infected at the same location over a seven-day period.

In a joint statement issued on Thursday evening, the education and health ministries said that they “wish to stress once again that the notion of a cluster is not synonymous with a source of infection.”

Clusters merely identify people who have tested positive for covid-19 in the same place, “even if the infection has occurred outside of this location,” they said.

The ministries gave a hypothetical example of three siblings who were infected during a family event. If they attend the same school, that school would then be flagged as a cluster.

According to the education and health ministries:

“… apart from a few rare cases, where doubts remain, no infection has been spread through a school; to date, we have no evidence of covid-19 transmission in a school setting in Luxembourg.”

The two ministries said they were jointly preparing “an in-depth analysis of the impact of covid-19 in schools” to be released at a later date.