NHS hospital laboratories will start testing swab samples from people who are displaying symptoms of coronavirus to ease the strain on Public Health England, which had been running all tests.

The move will double the number of tests that can be done every day in the UK from 2,000 to 4,000, reducing the load on PHE staff and facilities. Just under 25,000 people in Britain have now been tested.

Concerns had been expressed that the time taken to get test results back from swabbed patients had slipped in recent weeks from one or two days – PHE’s target – to as much as four days.

A&E staff have voiced unease that not all patients advised to self-isolate after having a test in a “pod” at a hospital will do so until they receive their test results. They were also concerned about the psychological impact of delays in getting a positive or negative diagnosis.

Prompt testing of samples taken from patients’ noses and throats is vital in the effort to limit the impact of the virus. It is intended to contain its spread by identifying carriers and allowing people with whom they have been in close contact to be traced and tested, who can then be quarantined.

Q&A How can I protect myself and others from the coronavirus outbreak? Show 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.

One A&E consultant said: “A delay of four days is not necessarily a risk to patients, who are advised to contact NHS111 if they get any worse in the interim. However, the delay can lead to anxiety and people breaking self-isolation.”

One A&E nurse said the average turnaround for tests they were taking had stretched to four or five days. “Tests are taking longer than anticipated to be processed by the labs, I assume because of the sheer volume of samples they’re receiving. We’re being instructed to tell patients that they will often hear from PHE within 48-72 hours of the swabs if they are clear. During this time they should self-isolate,” the nurse said.

“The problem we are facing is that samples are taking longer than expected to be processed and people may not continue to self-isolate after the recommend time. Subsequently, if they are positive, they are then going back out into the general population.”

The introduction of NHS testing will be phased in over the next few weeks. Large hospitals such as King’s College hospital in south-east London will start analysing samples on behalf of other hospitals in their area.

When coronavirus was first detected in Britain in late January, PHE tested small numbers of samples from suspected cases at its main laboratory in Colindale, north London. As more and more people presented with potential symptoms, the number of laboratories undertaking PHE’s diagnostic test for the virus was increased on 10 February to 12 across the UK.

The laboratories have increased staff working hours to 12 hours a day, seven days a week, while machines test samples overnight.

PHE confirmed that NHS laboratories were now being brought in to help. A spokesperson said: “In the first instance, we are working to roll out the test to more labs rather than having staff on site 24 hours a day. We are still operating within capacity.

“Our capacity is closer to 2,000 a day across the UK at the moment and will be extended to around 4,000 in the coming weeks.”