Investigations are continuing into how an Auckland Airport worker who cleans aeroplanes that arrive from both red and green-zone countries caught Covid-19. Genomic testing linked the infection to a traveller who arrived from Ethiopia via the United Arab Emirates on a plane the worker later cleaned. So, what do we know about how the virus behaves in these environments, and the risks? Dr Joshua Freeman, the clinical head of microbiology at the Canterbury DHB's laboratories, and an expert in viral aerosols, spoke to Corin Dann.