Mystery cases, faster onset of infectivity trigger alarm bells

THREE cases of COVID-19 in NSW are under investigation as health authorities grapple with the possibility of having missed a chain of transmission and evidence emerged of the virus becoming infectious at “unusual” speed.

NSW Chief Health Officer Dr Kerry Chant said she was concerned authorities could have “missed a chain” of transmission if the mystery cases are not linked to the Crossroads Hotel cluster, which on Thursday rose to 40 people.

It comes as one of the nation’s top doctors warned of at least one case in NSW that showed symptoms within 24 hours of being exposed – a major development labelled “unusual”.

“We are concerned when we find cases that can’t be linked back because it does indicate that we may have missed a chain,” Dr Chant said.

NSW recorded 10 new cases of coronavirus in the 24-hour period to 8pm on Wednesday, of which four were returned travellers in hotel quarantine, three were linked to the Crossroads Hotel outbreak and three are under investigation.

National Deputy Chief Medical Officer Michael Kidd said at least one case in NSW had become infectious within 24 hours of being infected with COVID-19 – much faster than what experts have seen, with people usually becoming infectious about three days after exposure.

“People usually develop symptoms within 5-7 days of infection but may be infectious one or two days before symptoms develop. As we see large numbers with COVID-19 infected in Australia, we are starting to see examples of people with early infectivity.”