All schools on the Isle of Man will close from the end of Monday to most pupils, the government said.
Only the children of those "critical to the island's coronavirus response" will then be able to attend, Chief Minister Howard Quayle said as the number of positive cases rose by three to five.
All ports will close to non-Manx residents from 09:00 GMT on Monday.
Pubs, restaurants and cafes will shut from midnight on Sunday but can still offer takeaway and delivery services.
Health Minister David Ashford said the latest patients to have tested positive for the disease were self-isolating and not in a "hospital setting".
The island's five secondary schools, along with nine primary schools that have special needs educational support, would remain open to the children of those who were "critical to the island's Covid-19 response", said Mr Ashford.
'Follow the advice'
He said that while two of the new patients had "travel history similar" to the previous confirmed cases, one had "no travel history".
Mr Ashford said this meant the virus had been "contracted somewhere in the community" on the island.
"This community case fundamentally changes the situation and I cannot stress enough how serious it is that people follow the public health advice that is out there."
Those who have underlying health conditions, are pregnant, or are over-70 have been asked to self-isolate if possible.
The Isle of Man already has laws that require all new arrivals at the ports to self-isolate for 14 days or face prosecution.
The entire population has been advised to practise social distancing and maintain excellent hygiene standards.
Other new measures announced by the Manx government include:
- The closure of the Wildlife Park, the National Sports Centre, regional swimming pools, and all gyms and fitness centres
- The cancellation of the Manx Youth Games in May
- The scrapping of April's Isle of Man Sports Awards
Speaking at the government's daily briefing on the pandemic, Chief Minister Howard Quayle said he could "not overstate the challenges" the impact of the virus would have on the Manx economy.
Measures to support businesses and workers will be announced by Treasury Minister Alfred Cannan on Monday morning.
At Saturday's briefing, the island's medical director Rosalind Ranson urged everyone to abide by the government's advice to prevent Noble's Hospital from becoming "overwhelmed".
Dr Ranson said, without isolation, the "spread of infection will become exponential in growth and it will overwhelm our health and social care system".
She said: "The lives of others depend on you. There's only so much that medicine can do."
Of 145 tests carried out so far, there have now been five positive cases.
The island's health department is awaiting the results of a further 150 tests from UK laboratories.