The virologist said many people justify breaching lockdown rules.
He said: “Some people use inconsistencies in the rules as a justification to refuse all rules completely.
“There is also a loss of control, because we are suddenly confronted by all these restrictions, and nobody can clearly tell us when and how they are going to end.
“In a country like the UK, we are not used to this level of uncertainty.
“I think clear targets would help here. If there was a clear decision to bring Covid-19 numbers down to one case per million per day, which then enabled us to ease restrictions and to control individual outbreaks locally, we would all have a common aim that we could achieve together.
“In the absence of such concrete targets, many people seem to focus rather on what they are still allowed to do and making the most out of this, instead of asking how they can reduce their individual chance to catch and transmit the disease.
“Such a scenario can be a recipe to spread Covid-19 within the rules, even without breaking them.”