Director of Public Health Dr Nicola Brink said the next 48 hours was key to understanding the extent of the outbreak, which has disrupted many parts of island life.
The outbreak started on Friday with three confirmed cases. Currently 25 of the 43 active cases in the Bailiwick of Guernsey are in the northern island.
Since Friday about 800 tests have been carried out in the island – which has a population of about 2,000 people.
That includes symptomatic testing, surge testing and surveillance testing.
Some direct contacts of cases are being required to self-isolate, which has impacted local businesses.
The Age Concern charity shop in St Anne’s, Divers Pub at Braye, The Sailing Club, the Cantina No 6 restaurant, Alderney Farm Shop and Moorings pub were all closed yesterday.
Staff shortages due to some employees having to self-isolate was the cause of some of the closures.
However, Braye Beach was still busy with visitors.
Among the positive cases identified in Alderney was a child who attends St Anne’s School.
As a result, about 30 children who were at school last week have been identified as contacts of the positive case.
These children are in reception, Year 1 and Year 2.
They will have to have a day 13 mouth swab test and also stay at home, except for socially-distanced exercise.
Dr Brink said very high numbers were being tested to understand where it had spread to, so it could be controlled.
‘I realise this is causing some anxiousness in Alderney, which had only seen one positive case throughout the pandemic before this cluster,’ she said.
‘We also know that for those who are having to self-isolate, because they are not fully vaccinated or because of the nature of their work, this can have a particularly big impact as many people in Alderney work not just one but two or three different jobs.
‘The next 48 hours will be key in telling us the full extent of the situation in Alderney.’
She was confident that with the community’s help, the outbreak would be brought under control.
Alderney States member Bill Abel, who is also member of the Civil Contingencies Authority, said the outbreak had hit the community hard.
‘There’s no doubt this outbreak has rocked our community after more than 18 months with no community seeding and the impact on the community and in particular our younger working people is substantial,’ he said.
‘We have had fantastic support from the Guernsey and Alderney health and medical teams and I am sure the community will support me in thanking them for their hard work and dedication.’