Covid: 'Stopping to talk to others helps spread infection'
"Every time you stop and talk to someone... then you've just had a potential transmission event."
Dr Chris Williams, of Public Health Wales, has warned that a rise in cases before the firebreak lockdown in Wales was mostly caused by people chatting indoors, in their homes, pubs and restaurants.
He said most of the cases were not caused by venues breaking rules, but people's desire to talk to each other.
"Speaking to people is something we find very hard not to do," he said.
"I think that's part of the problem because we don't see that as a bad activity."
His data surveillance team have been looking at cases and trying to spot how the virus spreads.
Their work could be key in informing any future lockdown measures.