Covid-19 in South Africa: It’s time to ditch quarantining and contact tracing

When a new epidemic rears its head, one thing that public health officials sometimes try to do is to impose a quarantine. Quarantining is when individuals who have been exposed to an infection, but who aren’t yet sick, are kept apart from the rest of the population, so that if they are incubating the disease, you can catch it early and limit its spread to others. 

This is distinct from “isolation”, which is when an infected individual is separated from non-infected people. Quarantines are for healthy contacts of a case; isolation is for the case itself.

Quarantines date back to at least the 14th century, where ships arriving at Mediterranean ports from plague-ridden areas were required to anchor offshore for a period of 30-40 days to ensure that no one aboard was incubating the infection. The word quarantine actually comes from the Italian for “40 days”: quaranta giorni. 

By their nature, quarantines are drastic measures, and they’ve proved controversial ever since their origin. The psychological toll of separation from one’s friends and family can be burdensome, and there are often financial repercussions to being forced into quarantine too. Restricting people’s movement is obviously also a violation of their usual freedoms of movement and association, and sometimes quarantining individuals can have the undesirable side-effect of making them easy targets for scapegoating. 

So the downsides are obvious — but does quarantining work? Historically, it’s a mixed bag. Researchers from the National Academies of Science, Engineering, and Medicine reviewed some of the evidence for it, and found that quarantines probably did work for some diseases, like ebola and Mers (Middle Eastern Respiratory Syndrome; a disease that ten years ago briefly threatened to become a pandemic), but not for other diseases, particularly respiratory pathogens such as pertussis or measles. 

Whether or not quarantines are effective depends in large part on the particular characteristics of the organism, its transmission dynamics and the disease itself. For some diseases, quarantining really can help contain an epidemic, whereas for others, no matter how good your quarantining is, you barely hamper the pathogen’s spread at all. 

One of the key variables is whether or not the cases can be rapidly and reliably identified. This makes sense — if you aren’t finding enough of the cases in the first place, then you obviously aren’t able to identify the contacts of those cases who need to go into quarantine. 

It turns out that this simple requirement dooms any practical attempt to limit Covid-19 through quarantine though. Why? Because based on extrapolations from studies in South Africa, we barely identify one-tenth of the actual cases. 

There are at least three reasons for this. 

The first is the high proportion of cases that don’t display any symptoms (i.e. are “asymptomatic”). 

When Covid-19 first arrived on the scene, it was thought that pretty much all infections resulted in symptoms. This is why things like temperature checks were initially thought to be a good idea. But we now know that a large number of Covid-19 infections are totally asymptomatic. The proportion probably varies depending on things like how old or immune-compromised the person is, and which particular groups you look at, but estimates typically vary from about 30% to over 80%. 

Testing for infection by SARS-CoV-2, the virus that causes Covid-19, is heavily skewed towards patients with symptoms though — if you don’t feel sick, why would you go and test? So almost all these asymptomatic cases are missed, and therefore none of their contacts can be quarantined.

The second reason is that many people don’t go and test even when they do feel sick. Perhaps you have only very mild symptoms, and think it’s “just a cold”. Perhaps you can’t afford a test (until this week in South Africa, a typical PCR test for Covid-19 cost R850, putting it well out of reach of most of the population), or even if you can afford to, you just find the price prohibitive. Perhaps it’s difficult to take time off work to get a test. Perhaps you live far away from the nearest testing station, and the cost and inconvenience of getting one puts you off the idea. Or perhaps you just don’t want to deal with the fact that you might have Covid. The point is, many people don’t get tested for Covid even when they do feel sick. 

And then, finally, even if you do decide to go and get tested, the test itself doesn’t always find the virus when it is there. 

The so-called “test sensitivity” of PCR-based tests varies depending on how thorough the swabbing is, and how far along in your infection you are, but is probably around 70% overall, and rapid antigen tests are even less sensitive.

So when you put those three reasons together, you can see why quarantining is a doomed strategy. We just don’t find enough of the contacts to quarantine, because we just don’t find enough of the cases in the first place. 

We can actually get some idea of how many people with Covid we miss, to put numbers to this all. Sero-surveys, which track antibody evidence of past Covid infection, indicate as much of three-quarters of the population (~45 million) has been infected during the first three Covid-19 waves, whereas the number of documented cases is less than one-tenth of that (3,167,497 on 14th December 2021). 

When you also factor in that the antibody tests may themselves miss some previous infections (antibodies tend to fade away with time), then it seems likely that we detect an even lower proportion of cases than that. Consequently, it’s only the minority of individuals who are exposed to viruses that are actually quarantining, even if fully adherent to the current regulations. 

There are other wrinkles too. 

For instance, in South Africa, the current advice is to only quarantine if you are a “high risk” contact, with high risk being defined as being within 1-1.5 metres for more than 15 minutes without adequate personal protective equipment (like a mask). But that definition was designed before we knew that SARS-CoV-2 mainly spread by aerosols, which are the microscopic particles that we exhale as we breathe and cough, and which can travel greater distances and remain circulating for longer periods of time.  

And the definition was also crafted before we had to contend with the far more infectious and transmissible variants such as Alpha, Beta, Delta, and now even the more transmissible Omicron variant. 

Put together, this means that even if quarantining could work in theory (it can’t, not for this virus), we’d still probably be quarantining the wrong set of people anyway, and achieving very little apart from inconveniencing people and disrupting economic, educational and other social activities.

Contact tracing

Once you understand all this then you can also see why contact tracing is futile too. 

At the moment, South African public health officials dutifully try to identify all the people each new Covid-19 case has come into contact with during the period in which they might have been infectious. But if quarantining serves no demonstrable public health purpose, then finding contacts to quarantine is ineffective by definition. 

It’s also grotesquely impractical. The average case may have 10-20 individual contacts per day, and a contact tracer may have to go back five or more days in looking for all the contacts. 

Things rapidly get pretty silly when you’re trying to deal with tens of thousands of new cases daily, as we currently are seeing. Near the peak of a wave, there can be over a million people to try to contact each day — a clearly ridiculous number. The human and financial resources that go into contact tracing are massive, and they serve no purpose when you are dealing with a disease that can’t be controlled through quarantining and isolation anyway. Such scarce resources are far better deployed in the service of public health goals that actually do work.

So much for the public health angle. What about on an individual level? 

If you’ve been sitting next to someone who’s just tested positive, should you still go and visit your elderly grandfather this weekend? Again, it’s important to realise that for every person who you sat next to who tested positive, there are probably at least another nine or 10 people who you sat next to this week who had Covid but didn’t know, or didn’t test. So focusing on the few cases that are diagnosed won’t have much of an effect. 

If you’re very worried, sure, you could postpone the visit until after 10 days have passed, but don’t forget that the best way to protect will always be vaccination, not quarantine, and that the downsides to staying away are also still present — such as a missed visit with a beloved relative.

Overall, the impact of the quarantine and contact tracing policies on the country, particularly during a wave of infections, is alarming. 

Currently, quarantining adds exponentially to the masses of healthcare workers who have already contracted Covid and had to go into isolation, a burden that threatens the integrity of the very healthcare system that these measures were designed to protect. Entire primary healthcare clinics have ground to a halt, and these policies have impaired almost every essential service, from police to government offices, to say nothing of the economic costs to individuals and to the country as a whole.  Quarantining is always a drastic public health measure that incurs massive social, financial, psychological, and societal costs. While it can be a valid strategy for certain diseases, Covid-19 simply isn’t one of them. Ironically, we’d be better placed to tackle Covid without it. Current quarantine and contact tracing policies need to be abandoned — urgently. DM/MC

Shabir A Madhi is the Dean, Faculty of Health Sciences and Professor of Vaccinology at University of the Witwatersrand, Jeremy Nel is an infectious diseases expert, University the Witwatersrand, Francois Venter is Professor of Medicine, University of the Witwatersrand.