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Covid-19 Expert Advice #1: How long should I isolate or quarantine for?

- The Scientists Collective

This is the first of a series of expert advisories on how to respond to Covid-19 which will be published from time to time by Maverick Citizen.

This series is co-written by some of South Africa’s leading medical scientists and academics, including some members of the Ministerial Advisory Committee (MAC) on Covid-19. Although not written for or on behalf of the MAC, much of whose important advice is being lost in the corridors of government, it is intended to provide practical life-saving advice based on the best emerging knowledge and evidence of Covid-19.

An infographic by the Ndlovu Care Group, using the information from this article, helping South Africa understand the difference between self-isolation and quarantine for Covid-19.

We are learning all the time, so it is highly likely that advice will change as we learn more about the virus, so keep an eye on any new recommendations. However, the basic principles explained in this series will stand and help inform your decisions.

“If I have Covid-19, how long should I stay away from work and self-isolate from other people?”

“If I have been in contact with someone who has Covid-19, for how long should I quarantine?”

“What should we advise workers, employers and their household contacts?”

It sometimes appears that the public is being given conflicting advice in media interviews, slide sets from the Department of Health that circulate over social media, and differences with guidelines from WHO and other countries. This has led to uncertainty and confusion for the public, employers and healthcare workers about how long we must isolate or quarantine in relation to Covid-19.

We are a group of clinicians, scientists, and other professionals, many of us Ministerial Advisory Committee members, who are unpacking guidelines to help the public, workplaces, employers and unions, as well as government departments to support a balanced return to relatively normal life as fast as possible while keeping people safe. We have tried to align to guidelines and simplify wherever possible. The scientific references we have relied on are listed at the bottom of this article.

It is highly likely that people reading this will need to isolate or quarantine themselves in the coming months, possibly multiple times, so it is worth trying to understand the reasons for doing so.

Keep in mind: SARS-CoV-2 is the virus, Covid-19 is the disease it causes.

First, the difference between isolation and quarantine, as used here:

  1. Isolation means that after you develop symptoms of Covid-19 and/or test positive for the SARS-CoV-2 virus, you need to stay apart from others so as to not spread the virus to them. This includes asymptomatic people who have a positive test.
  2. Quarantine means that after you have had a high-risk exposure to Covid-19 (ie, close and prolonged (more than 15 minutes) contact without prevention strategies (eg, wearing of face masks or good ventilation), you need to stop being in contact with people and stay apart. This is in case you have contracted Covid-19 from your initial exposure.

Practically speaking, both isolation and quarantine means separating yourself from others. The difference in how long you need to separate yourself is based on the science.

To summarise the recommendations:

  • You should isolate for 10 days after the start of suggestive symptoms (unless hospitalised, see below) or testing positive, and quarantine for 14 days if you are exposed to a high-risk situation.
  • There is no need for you to test if you are asymptomatic (unless you are being screened as a frontline healthcare worker).
  • There is also no need to test or retest at the end of quarantine or isolation periods.
  • Do not rely on a negative test result to say you are safe, especially if you may expose vulnerable people, like the elderly or people with chronic medical conditions or cancer.

Both isolate and quarantine mean stay at home; get someone else to shop for you if you can; try to keep away from people you live with and avoid all people in case you infect them. Open windows and wear a mask when you can’t avoid being in a space that others will use.

Obviously, quarantine transforms into isolation if you get symptoms. For practical purposes, they mean similar practical steps – stay away from people as best you can!

The 10 and 14 days advice above is a safe and very conservative recommendation, particularly in the case of the isolation guidelines. However, none of these rules are failproof and they may change as new information becomes available. As your best defence, you should continue to:

  • practise physical distancing
  • wear of a mask (covering both your mouth AND nose)
  • avoid crowds
  • wash hands frequently
  • wipe surfaces clean.

“Exposures” vary wildly and need some common-sense assessments. We present some case studies at the end, to help understand how much these can vary.

What is the reasoning behind the timelines?

Infection from SARS-CoV-2 starts with exposure to a person who is infectious. If you get infected, there is a period of a few days, called the incubation period (usually 2-4 days, but can be longer) in which you do not show any symptoms. After a few days of symptoms, you become less infectious, and (unless you were very seriously ill) 10 days after symptoms started you are very unlikely to be infectious (even if you still have some symptoms or test positive on the PCR tests, which shows dead virus).

There is greater confidence in the science allowing us to relax the previously used 14-day timeline for de-isolation. For people who do not require admission to hospital, the virus will not grow after nine days from the onset of symptoms, making it very unlikely that it will be able to infect anyone beyond this point. This is why staying away from people for 10 days protects them. The added four days for the 14-day quarantine period includes the incubation time. So, there’s generally no point in repeating tests in people who have had a positive test and are isolating.

In people who don’t have any symptoms and test positive, it is harder to know when infection started. In this scenario we recommend (to keep things simple) 10 days for such people (“asymptomatic infections”). However, please don’t test if you don’t have symptoms! You are wasting precious resources.

Another complication is that very ill people may be infectious for longer, so for them we start measuring once they are well on the road to recovery and off oxygen support. For everyone else, the start of symptoms is fine.

It is useful to start thinking of a clock (a calendar or diary is useful) – and these possible scenarios that will help guide 99% of your decisions:

  1. I am ill with symptoms that may be SARS-CoV-2 (cough, fever, sore throat, loss of smell/taste, etc –see here).
    • The 10-day clock for isolation starts from the day symptoms started.
  2. I am ill with symptoms that may be SARS-CoV-2 and tested positive on day 4 of symptoms. When will I be able to de-isolate?
    • The 10-day clock still starts from the day symptoms started.
  3. I have no symptoms but I got a test and the result came back positive 3-days later. When will I be able to de-isolate?
    • The isolation clock starts from when you had the test, not when you got the result.
  4. I have been exposed to someone who has tested positive or has been diagnosed with Covid-19, or I was in a high-risk situation (see below) and I am worried. How long should I quarantine for?
    • The 14-day clock starts from the last exposure.

Coming out of isolation or quarantine does not require a test unless you are a frontline healthcare worker (see below). Above all, if you do decide to rely on a test performed in private (the public sector does not perform tests for this reason), then please do not rely on a negative test to say that you are to interact with vulnerable people like the elderly or people with chronic medical conditions or cancer.

The test for SARS-CoV-2, which causes Covid-19

The diagnostic test we use for acute infection with SARS-CoV-2 identifies the genetic material of the virus and is termed a PCR (polymerase chain reaction) test. What we can learn from the commonly available PCR test is surprisingly complicated to interpret. Sadly, it means that we should not rely too heavily on the results because:

  • If the result is negative, you can still have the virus – it may be too early or too late (and you are no longer infectious) to detect the virus OR the sample has technical issues when being processed.
  • If the result is positive, it means you ARE infected, but confusingly, may not tell if you are infectious or not – as the test detects only one bit of virus (its genetic material), it doesn’t tell us whether that genetic material is sitting within a fully competent virus able to infect other people, or just left-over bits from being killed by our immune system. Indeed, towards the end of symptoms, virus present on PCR testing can’t be transmitted (“replication incompetent’’).

This sounds confusing (and it is), but it is important to understand that a negative test is not the best basis for deciding to isolate or not, or for ending isolation or quarantine.

The SARS-CoV-2 PCR test has been recommended in the past to know you are “safe’’ to return to work (including recommendations in government department guidelines) or to see your elderly parents. As you can tell from the above, this is not a good way to assess your risk, particularly since it can take several days to get test results, is expensive and ultimately proves unreliable if negative. Many countries have started to remove the recommendation for a negative test, appreciating how limited its practical use is.

As presented above, a time-based de-isolation period is much more practical and reliable. 

Another testing option involving serology (an antibody-based test) looks at the immune response to the virus rather than the virus itself. The problem here is that it takes days or even weeks to become positive. Furthermore, we do not yet know whether you get effective immunity (protection) after infection with this virus. Immunity may be possible in ways other than with antibodies, but there may be other parts of the human immune response that are important that we are not looking at. Additionally, protection from reinfection after you have had Covid-19 may be partial, temporary or zero – we do not yet know.

At present, this serology test has no role outside of research or surveillance settings. Talk of an ‘’immunity passport’’ is dangerous, in the absence of any reliable test (many appear to become negative again a few months after infection) or clarity whether immunity is even possible (the South African authorities are evaluating these tests).



Sadly, we do not yet know whether you get effective immunity from infection with this virus. So, whether you have been diagnosed before, or think you may have had Covid-19 previously, it does not help make isolation or quarantine decisions. This may change, but for now rather think of yourself as having no immunity to a future infection from a previous proven or suspected infection. As mentioned, serology tests are under evaluation, and should not be used to assess your own immunity. The rule is: the clock operates for everyone, irrespective of whether you have had Covid-19 previously.

What is a high-risk exposure?

Hopefully you know this by now, but for the purposes of understanding what constitutes exposure, we need to understand that SARS-CoV-2 is thought to be spread primarily through respiratory particles which are in the air we breathe, or which can land on our eyes, nose and mouth, when we are close to someone who is infected, for prolonged periods (more than 15 minutes), or in front of them (face to face and less than 1-2metres).

The respiratory particles can be transmitted from an infected person who talks, sings, coughs or simply breathes. Barriers such as masks can stop these particles from moving away from a person who has Covid-19, and wind removes them quickly, meaning that being outdoors or in a well-ventilated space, with people wearing masks, is much safer, while being with people indoors or in a vehicle, with closed windows, not wearing masks, all dramatically increase risks. Air-conditioning systems that recirculate air also recirculate infectious particles, making them risky.

Open windows and natural ventilation is best.

An easy way to think about this is to imagine yourself not wearing a mask in a closed room with someone else for 15 minutes. That is considered a significant amount of time in contact with the virus and constitutes a high-risk exposure. If you and the other person are wearing masks, it buys you more time. If the windows and doors are open, it buys you a lot more time. If the person is coughing, talking a lot or singing, these actions significantly increase your risk and cut down the time required for you to contract the virus.

It is possible to get infected in less time than 15 minutes, but is very unlikely. You will not have a significant exposure paying for your groceries, brushing past a runner who is not wearing a mask, or at an outdoor braai or picnic where everyone is standing more than 1m apart between each person.

You will be exposed if you are inside a taxi with closed windows, in an indoor place of worship that is crowded (less than 1m) and where people are singing, in a workplace that has poor ventilation or heaters on, or in a nightclub, for longer than 15 minutes with someone who is infected, and all the more if not wearing a mask.

Why do exposed health workers get different advice?

Health workers are in a difficult position – their work places them in a very high-risk scenario; they are absolutely essential to providing uninterrupted services, particularly in a pandemic; but they also have access to personal protective equipment, which gives some protection from infection, and also reduces the likelihood of them of infecting their patients.

Having them off for 14 days each time after a high-risk exposure would be catastrophic for the health system. As a result, obtaining a PCR test result is prioritised for healthcare workers, despite all its weaknesses. The recommendation here aims to balance all known factors.

Current Department of Health guidelines require health workers who remain asymptomatic seven days after a high-risk exposure to have a PCR test on day eight, which if negative, allows an immediate return to work. We believe that a balance of the science, the pressure on the health workforce, and the safety aspect could allow this to be dropped to a test five days after exposure with return to work if negative, so long as they are extra careful regarding the use of medical-level protective equipment at work.

Common scenarios that people face every day

Finally, here are some common scenarios relating to timing of isolation and quarantine that we encounter day-to-day. All are real cases and the persons involved have given us their consent to use them.


Someone with no symptoms goes to a drive-through testing station. The result is positive. How long do they have to isolate themselves for?


First of all, please stop testing if you do not have symptoms! As explained above, it does not help with decision making. But now we have the test, 10 days from the date of the test.


A woman tests positive after she starts coughing. She self-isolates for 10 days, but on the 10th day her husband, who lives with her, also tests positive. When can she go back to work?


It is likely that she passed the virus to her husband some days before, and that she is now recovering. She can go back to work.

He should isolate and must observe the 10-day isolation from the start of his symptoms (or the day of his test if he has had no symptoms).

The test on him, especially as it probably took a few days to come back, adds almost no value here – he could have quarantined for 14 days from the last close contact with his wife, if she was isolated from everyone except him.


A family of six, with one elderly person, one diabetic, and two children (one aged four, one six), are informed that their domestic worker, with whom they had close contact, is ill in hospital and tested positive for Covid-19.  The family enters quarantine but the 6-year-old gets sick and gets tested positive. What should the family do?


The key question here is, how do you protect vulnerable members of the family from a member who is infectious to them? Isolation within family units is often difficult, especially with young children who may not understand physical distancing.

It seems the most effective way to deal with this is to either:

  • Ideally, quarantine the elderly and diabetic family members (higher-risk persons) elsewhere;
  • Distance them within the household as much as possible – stay in one room, open lots of windows, and wear masks).

Common spaces such as kitchens and bathrooms should be ventilated as much as possible; wait for some time (30 minutes with lots of windows open) after an infectious person has used these areas, and wipe surfaces.

Flush the toilet with the lid down.

If symptoms develop, watch them closely – any difficulty in breathing should trigger a trip to the hospital.


A couple living with a 2-year-old child all have symptoms and test positive over a period of a week. One partner and the child get better, but the remaining partner has persistent symptoms. The well partner needs assistance with childcare from her elderly parents – when can the two parents leave the house safely?


The 10-day rule above applies.

Even the partner with symptoms (as long as improving) could de-isolate after this period.

But be aware that being elderly is high risk (as is diabetes, hypertension, obesity and HIV, as well as other chronic conditions), and being as careful as practical around the elderly parents seems sensible.


A domestic worker is involved in looking after an elderly man with Covid-19. How long should she quarantine for?


14 days from her last close contact.


Someone at work tests positive. When should the employer test everyone?


Don’t test ANYONE. Assess people’s exposure to the case, and, if significant (see above), quarantine them for 14 days. If not, carry on with the usual precautions.

We have found the first cases are often the wake-up call in the workplace you need, sadly, for employees and managers to take this seriously (tea rooms are notorious for people to relax their guard).

Use the opportunity this case affords to ensure strong adherence to interventions that we know work – physical distancing in the workplace, universal masking, proper hand hygiene, regular cleaning of routinely used surfaces, and checking for symptoms on a daily basis with employees staying home and seeking medical advice, if symptoms develop.


Someone is returning from the US, how long should they quarantine for?


Current SA guidelines forcibly quarantine people for 14 days on return from international flights. This was based on when our epidemic was largely linked to people infected in other countries. It does not make sense now we have such widespread infection.

Air travel in general appears relatively safe, and it is unclear whether local and international travel risks are different (coming from a low-risk area may be safer than coming from an area in SA where the pandemic is raging). These guidelines need updating – but if you want to be supersafe, treat the travel as an exposure and quarantine for 14 days.

This article was first published in the Daily Maverick/Maverick Citizen.

*The Scientists Collective: Dr Nomathemba Chandiwana, Professor Francois Venter, Dr Joana Woods, Dr Bronwyn Bosch, Mohammed Majam, all at Ezintsha, University of the Witwatersrand; Dr Jeremy Nel, University of the Witwatersrand, Professor Marc Mendelson, University of Cape Town; Prof Shaheen Mehtar, University of Stellenbosch, Dr Elijah Nkosi, Dr Morgan Chetty, both family doctors; Professor Yunus Moosa, University of Kwa-Zulu Natal; Professor Shabir Madhi, Respiratory and Meningeal Pathogens Research Unit, University of the Witwatersrand; Dr Halima Dawood, University of Kwa-Zulu Natal; Dr Lucille Blumberg, National Institutes of Communicable Diseases; Professor Lucy Allais, Department of Philosophy, Wits Centre for Ethics, University of the Witwatersrand; Professor Glenda Gray, South African Medical Research Council; Professor Andy Gray, Division of Pharmacology, Discipline of Pharmaceutical Sciences, University of KwaZulu-Natal; Dr Angelique Coetzee, South African Medical Association.

The advisory above has taken account of the following published studies:

  1. Wolfel R, Corman VM, Guggemos W, Seilmaier M, Zange S, Muller MA, et al. Virological assessment of hospitalized patients with COVID-2019. Nature. 2020.
  2. Liu Y, Yan LM, Wan L, Xiang TX, Le A, Liu JM, et al. Viral dynamics in mild and severe cases of Covid-19. Lancet Infect Dis. 2020;20(6):656-7.
  3. Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z, et al. Clinical course and risk factors for mortality of adult inpatients with Covid-19 in Wuhan, China: a retrospective cohort study. Lancet. 2020;395(10229):1054-62.
  4. Xu K, Chen Y, Yuan J, Yi P, Ding C, Wu W, et al. Factors associated with prolonged viral RNA shedding in patients with Covid-19. Clin Infect Dis. 2020.
  5. Bullard J, Dust K, Funk D, Strong JE, Alexander D, Garnett L, et al. Predicting infectious SARS-CoV-2 from diagnostic samples. Clin Infect Dis. 2020.
  6. Arons MM, Hatfield KM, Reddy SC, Kimball A, James A, Jacobs JR, et al. Presymptomatic SARS-CoV-2 Infections and Transmission in a Skilled Nursing Facility. N Engl J Med. 2020;382(22):2081-90.
  7. Lui G, Ling L, Lai CK, Tso EY, Fung KS, Chan V, et al. Viral dynamics of SARS-CoV-2 across a spectrum of disease severity in Covid-19. J Infect. 2020.