Work to trace the source of the outbreak in Aberdeen is under way, said the Health Secretary.
It comes as Nicola Sturgeon confirmed the number of cases linked to the cluster in Aberdeen has increase to 79.
A further 30 cases are under investigation and may be linked to the outbreak. A total of 233 close contacts have also been identified.
However, the difficult job of tracing the source of the outbreak – and identifying the “trigger case” – is under way according to the Health Secretary Jeane Freeman.
She added it was unlikely that one person had visited all 28 bars on the list released by NHS Grampian.
Speaking to the BBC’s Good Morning Scotland she said: “In an outbreak like this it is very difficult to identify, if you like, the trigger case, is how it would be described.
“One of the ways that we can do that and this work is unde rway, although it takes some time, is the genome sequencing, that we do. “We’ve talked about this before and that traces back all the different strands of the virus and identifies where it started.
“So that work will get under way, but at this point it is not clear and that’s partly because of the nature of this particular outbreak and the complexity of it.
She added: “It is unlikely that one person has been to all 28 or so venues that have been named. What is more likely is more than one person has been to more than one venue and that is part of the complexity of this.”
“If you think about some of the other outbreaks we have responded and traced right through to the end of the transmission chain, in some ways they’re all very important, but in some ways they have been less complex than this, which is largely centred around the nighttime economy in Aberdeen.”
“So it is complicated to know exactly where everyone has been and that’s part of the test and protect operation which of course we need to remember is still under way, we’ve not concluded this yet.”
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