Public Health England has said it is not advising that schools shut in an attempt to stem the spread of coronavirus.

The organisation’s medical director, Paul Cosford, said: “Schools have to take difficult decisions given the complexity of issues that they are facing. What I would say is that our general advice is not to close schools.

“What we are clear about is if you have been in the area of northern Italy of concern and you have symptoms – it is a cough, shortness of breath or fever – then you do need to self-isolate, you need to phone NHS 111 and await advice for further assessment or testing.

“Of course if you’ve been to one of the specific towns that are identified by the Italian government and essentially closed down, then our advice and requirement is to self-isolate anyway.”

He said Public Health England (PHE) was available to talk to schools about their “specific circumstances” and “help them make the right decisions for them”.

At least a dozen schools have sent staff and pupils home to self-isolate for 14 days after returning from half-term trips in northern Italy. In Italy, 323 people have tested positive for the virus and 11 have died.

A spokesman for Trinity Catholic College in Middlesbrough, which was closed after pupils returned from a skiing trip in northern Italy, said this was so the school could undergo a “deep clean” given that pupils and staff had returned on Monday and the official advice had not been issued until Tuesday. “There had been the potential that the total school population had been exposed. Even though it was minimal, there was still the potential risk,” they said.

Cosford acknowledged that schools had “difficult decisions to take given the complexity of the issues” and any action should be based on their specific circumstances and what was best for their students, staff and parents. But he reiterated that there was definitely no blanket advice from PHE that schools should close.

PHE classes the area including Milan mostly as “category 2” in terms of Covid-19 risk. The detailed advice states in part that students returning from the region without symptoms should continue going to school as normal.

The health secretary, Matt Hancock, has said people who have been anywhere in Italy north of Pisa should self-isolate if they develop flu-like symptoms on their return to the UK.

The official Foreign Office advice has been changed to advise against “all but essential travel” to 10 small towns in Lombardy and one in Veneto, which are currently in isolation due to the ongoing outbreak.

So far 13 people have tested positive for the virus in the UK but have not suffered any major setback to their health as a result.

Cosford added that PHE was heightening its vigilance because of the apparent spread of the virus outside China. As well as monitoring anyone who meets the criteria – they have been to a country of concern and have symptoms – it is working with 11 hospitals across the country and 100 general practices to undertake random testing of patients who display similar symptoms but have not travelled to a country of concern.

Q&A How can I protect myself and others from the coronavirus outbreak? Show Hide The World Health Organization is recommending that people take simple precautions to reduce exposure to and transmission of the coronavirus, for which there is no specific cure or vaccine. The UN agency advises people to: Frequently wash their hands with an alcohol-based hand rub or warm water and soap

Cover their mouth and nose with a flexed elbow or tissue when sneezing or coughing

Avoid close contact with anyone who has a fever or cough

Seek early medical help if they have a fever, cough and difficulty breathing, and share their travel history with healthcare providers

Advice about face masks varies. Wearing them while out and about may offer some protection against both spreading and catching the virus via coughs and sneezes, but it is not a cast-iron guarantee of protection Many countries are now enforcing or recommending curfews or lockdowns. Check with your local authorities for up-to-date information about the situation in your area. In the UK, NHS advice is that anyone with symptoms should stay at home for at least 7 days. If you live with other people, they should stay at home for at least 14 days, to avoid spreading the infection outside the home.

“This will tell us whether there’s a risk of infection more widespread than we think there is,” he said. “We don’t think there is at the moment but if we do get to the point of more widespread infection across the country, it will give us early warning that that’s happening and that’s very important for us to be able to move to the next phase should we need to.

“If we do get to the point of more widespread infection, we will monitor that as it develops, we will take the best scientific advice as to how we may be able to delay transmission further and if that includes actions to isolate more widely then of course we will do that.

“But I think at the moment that is unlikely. If we do see more widespread infection we need to do all that we can to delay that onset so that at a point where it gets to greater pressures that the NHS is through the winter period and more able to deal with extra cases that may arise.”

The Department of Health has also added Iran, Vietnam, Cambodia, Laos, Burma and parts of northern Italy to the list of places where travellers need to follow clinical advice.