Can you still test positive for Covid after 10 days? How long infection can last - and when to leave isolation

Covid testing rules have been changed in the UK to address mass staff shortages caused by people self isolating

Covid-19 case numbers reached record highs over the past few weeks, fuelled by the Omicron variant.

An estimated 3.7 million people in the UK had coronavirus in the week ending 31 December, up from 2.3 million in the week before and the highest number since comparable figures began in autumn 2020, according to the Office for National Statistics (ONS).

It is possible to test positive Covid-19 for weeks, or even months (Photo: Shutterstock)It is possible to test positive Covid-19 for weeks, or even months (Photo: Shutterstock)
It is possible to test positive Covid-19 for weeks, or even months (Photo: Shutterstock)

Coronavirus testing rules have also been changed to help shorten self isolation periods, enabling people to get back to work sooner.

From 11 January, asymptomatic people in England who test positive on a lateral flow device (LFD) no longer need to get a confirmatory PCR test and so can start isolation immediately.

A similar system has already been implemented in Northern Ireland, Scotland and Wales.

But what do rules say about leaving isolation if you still test positive after 10 days? Here’s what you need to know.

Can you still test positive for Covid after 10 days?

Yes, it is possible to test positive Covid-19 for weeks, or even months in some cases, according to Gavi, The Vaccine Alliance.

However, people should not remain contagious for very long, even after a positive result.

It can take between five and six days on average for symptoms of Covid-19 to appear, although some people can start to feel unwell from one to 14 days after infection.

The length of time it takes for a negative test result to appear after infection will depend on how severe symptoms are.

It can also depend on the test itself.

A PCR test is much more sensitive and seeks out parts of viral genetic material (RNA) which can remain in the body long after the infection is over and coronavirus has been cleared.

By comparison, lateral flow tests look for viral proteins (antigens) and are less sensitive, so are less likely to give a positive result days after first infection.

If you test positive on a PCR but negative on a lateral flow, it is likely you are not infectious and have just residual virus RNA.

Studies suggest that PCR tests start to detect the virus around one to three days before symptoms start, which is when the viral load will be highest. After this point, the amount of virus in the body gradually declines until it can no longer be detected by PCR.

Asymptomatic people can typically test positive for one to 14 days, while those with mild-to moderate disease will often continue to test positive for seven days or more.

Lateral flow tests need a higher viral load to record a positive result, which is why they often only identify people during their most infectious period, according to Gavi.

The European Centre for Disease Prevention and Control (ECDC) said that adults with mild to moderate symptoms remain infectious no longer than 10 days after symptoms begin, regardless of the variant.

But adults with severe to critical illness, or severe immunosuppression, can remain infectious for up to 20 days after symptoms start.

However, evidence suggests people with Covid-19 who have been fully vaccinated can have comparable amounts of the virus in their body as someone who is unvaccinated, but they are less contagious overall.

When can I leave isolation?

The self-isolation period starts immediately from the onset of symptoms, or from when a positive lateral flow or PCR test was taken if you do not have any symptoms, and the next 10 full days.

If you get symptoms while you are self-isolating, the 10 days restarts from the day after your symptoms started.

However, recently introduced rules state that you can stop self-isolating after seven days if you take a rapid lateral flow test on day six and seven of your self-isolation period and

  • both of these tests are negative
  • the tests were take at least 24 hours apart
  • you do not have a high temperature

These rules now apply across the UK.

If you do a rapid lateral flow test on day six and the result is positive, you should wait 24 hours before you take the next test. If this also comes back positive, it is advised that you remain in isolation for the full 10 days.

There is no change to the guidance for unvaccinated contacts of positive Covid-19 cases, who are still required to self-isolate for 10 full days after their date of exposure to the virus.

If you still test positive after 10 full days and no longer have any symptoms, or you just have a cough or changes to your sense of taste or smell, you are legally allowed to leave isolation.

This is because these symptoms can last for several weeks after the infection has gone.

The only time you will need to continue isolating after 10 days is if you still have a high temperature or fever, or are feeling unwell.

In this case, you should continue isolating and seek medical advice.

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