A school in Melbourne’s north-west has been closed after a student tested positive for coronavirus, a week after a teacher was confirmed to be infected.

The student at Keilor Downs College acquired the infection through a known source, Victoria’s chief health officer Brett Sutton said on Friday.

“The student probably was infectious on-site on the 26th of this month and was notified yesterday,” he said.

Professor Sutton said the student was infectious when he attended school on Tuesday, May 26 – the day most students returned to face-to-face learning in Victoria.

Contact tracing is being conducted at the school and any close contacts of the student will be asked to self-isolate.

“It will probably apply to all of the classes that student was in,” Professor Sutton said.

On Tuesday, a teacher at the school was confirmed to have contracted the virus, but he had been working from home.

Students from Taylors Lakes and St Albans who attended a VET class with the Keilor Downs student on Tuesday have also been asked to self-isolate. Those schools have not closed.

Those students, as well as any other known contacts, will also enter quarantine.

The case was among seven new COVID-19 infections recorded in the state on Friday. Three were discovered through routine testing, two in returned travellers in hotel quarantine and two cases are being investigated.

It brings Victoria’s total number of cases to 1634, about 70 of which remain active.

Premier Daniel Andrews said despite signs the virus’ spread was slowing in the state, it was important for people to keep working from home if they could.

“We can’t have a situation where our public transport system is running at 100 per cent capacity,” he said.

“Having too many people in close contact … that will lead to a second wave. That’s what we’re trying to avoid.”

From Monday, the obligation for employers to keep their staff working from home will be included in Professor Sutton’s directions.

That means businesses could be fined for not enabling staff to continue working from home.

“I don’t think we’ll get to that,” Mr Andrews said.

Almost 6000 Victorians have been fined for breaking coronavirus restrictions, triple the rate of any other state.

But as restrictions ease, only one person has been fined by Victoria Poice this week.

More than 2500 spot checks at homes, businesses and non-essential services have been carried out by police since Sunday.

-with AAP