COVID-19: Can recovered patients get re-infected?

“There is still so much that we do not know about SARS-CoV-2, the virus that causes COVID-19.”

Recently, COVID-19 threw a curve-ball. There were reports that patients who had previously tested negative were testing positive again. This would go against the expectation of the scientific community that once a person recovered from the disease, they would have some form of immunity from the disease. So why is this happening?

There are three possible explanations for this observation, and no, none of them considers a re-infection as the underlying reason:

  1. How PCR works and what it tests
  2. Sensitivity of the COVID-19 tests
  3. The type of test whether PCR or antibody

PCR works by amplifying and identifying the genetic make-up of an organism. In other words, it looks for genetic material in the sample and returns a positive result if found. This is by far the most reliable test across diseases as it looks for the actual presence of the causative agent. The problem is, it doesn’t distinguish between viable and non-viable (“dead”) genetic material. The leading theory around those who turn positive after turning negative is that what is being picked are non-viable genetic remnants of the SARS-CoV-2 virus. In this case, there is no relapse and the persons are not expected to be contagious. Attempts to grow the virus from such persons in the lab have been unsuccessful supporting the argument that the material is non-viable and non-infectious.

The second possible reason bears an inherent worry: the sensitivity of medical tests. Sensitivity, in simple terms, is the likelihood of a test returning a positive result in a situation in which what it is testing for is present in the sample being tested. Doctors know that tests are rarely absolutely sensitive. In-fact, separate from COVID-19, this one property of tests has been a common cause of friction between patients and doctors for decades: talk of “misdiagnosis” and wrong treatment come to mind. Anyway, several factors affect the sensitivity of tests: the test itself, the stage of the disease (are there many viruses or few viruses in the body), the sample used, the technique of collecting the sample, the handling of the sample and many other factors. In the context of COVID-19, samples may be obtained from the nose or from the lungs. The sensitivity of the COVID-19 RT-PCR testing is reported to range from 55% and 70% for nasal samples, while lung samples bear sensitivities of between 77% and 90%. What this means is that between 10% and 45% of those tested will return a negative result while in fact they are positive. This is what is called a false negative. WHO has issued a guideline requiring that to be declared negative, a person recovering from COVID-19 must undergo two PCR tests done at least 24 hours apart.

Unfortunately, a patient with a false-negative test can still spread the virus.

The third possibility is the least likely. This is a situation in which testing agencies mix PCR tests (usually from nasal swabs and lung secretions) and antibody tests (usually from blood). I say this is least likely because I trust that all testing agencies around the world know enough not to do this. Whereas PCR tests looks for material from the virus, the antibody tests looks for the body’s response to the virus. Antibodies are what the body produces to fight infection and these often persist for years after the infection has cleared. A positive antibody test shows that one has ever been exposed to the virus but does not confirm that one has an actual ongoing infection (there are complexities around IgG and IgM but that’s technical stuff for doctors). Therefore, performing an antibody test on a patient who has recovered from COVID-19 is most likely to return a positive result even when the patient doesn’t have the disease.

A key point to note is that most rapid tests and home-testing kits are antibody tests. It means that those who will have recovered from the disease should brace themselves for a positive test all the time every time. The good news is that such a positive test is actually a test of immunity. Bear in mind that the value and longevity of such immunity is still under study. A patient with a positive antibody test but two negative PCR tests at least 24 hours apart is unlikely to be infectious.

I hope this information helps. Do share and leave a comment. You have my permission to copy, paste, publish, any or all of this material provided you accurately cite the source.

Dr. Victor Ng’ani

Please follow and like us:

TO WAKE UP OR NOT TO WAKE UP, THAT IS THE QUESTION FOR AFRICA.

TO WAKE UP OR NOT TO WAKE UP, THAT IS THE QUESTION FOR AFRICA.

My two daughters are awesome. One of their latest joys is story-telling. It reminds me of our time growing up when stories were all the rave. One particular one comes to mind: this man, up a tree, on one branch is a leopard walking towards him. On the other branch a huge, poisonous snake, also hissing and making it’s way, not slowly but rapidly towards the man trapped in peril. When it would seem his best hope would be to jump down from the tree and try to flee, it somehow turns out that there is a lion at the foot of the tree, roaring at him, staring intently, waiting for him to get down. There were no hyenas when I was told this story, but I will throw them in for good measure. Yards off behind the lions, a pack of hyenas surrounded the tree, all round, hoping against hope that somehow beyond the leopard, snake and lion, something would be left of the man in existential peril for them to take a bite of. Indeed to us as children, it seemed as though there was no way out of this nightmare for this man. Except, being a nightmare, all the man had to do to get to safety was to wake up.

COVID-19 is ravaging countries across the globe and has possibly changed forever our way of life as we know it. Whereas countries such as Italy are presented learning points on lack of adequate preparation, Africa is in a particularly perilous position. Years of neglect have left most health systems in shambles. We barely manufacture anything: some of the most basic personal protective equipment we require is imported. We have an insane shortage of healthworkers, but that statistic is only believed by healthcare workers: the rest of us seem to view it as routine psychobabble and rants of elitist and entitled doctors. American and European car manufacturers are changing their production lines to produce critical medical equipment such as ventilators: Lamborghini, Ford and quite a few others. Within weeks of being reported, some Western and Eastern Countries developed testing kits for detecting SARS-CoV-2, the virus that causes COVID-19. Studies are underway looking into potential vaccines and treatment options. The US of A is able to provide 2Trillion dollars US as a stimulus package to help mitigate the effects of COVID-19, while many African families are faced with no more than tough times, job losses and hunger. Should treatment be found, we have no reason to demand that Western countries ignore their populations and remember us. They won’t. In all this, we, as Africa, are largely waiting for our benefactors to spare some left-overs for us. There are videos alleging that Africans are being evicted from homes and hotels in China for whatever reason. One friend was considering importing N95 masks from China to help alleviate the shortage in Kenya and also help fight the profiteers who have priced these masks way out of reach of most healthcare institutions. Yet another friend in the clearing and forwarding business advises new importers of masks not to try doing so unless they are willing to part with “facilitation fees” for the customs officers at the inland container depot in Kenya. Even without COVID-19, try buying anything from Amazon: the American whose income and purchasing power is much higher than that of an African doing the same job will buy the same product for half the price, while the African pays 100% more in the name of shipping and taxes. That being in this surreal period of a most dangerous outbreak. It would seem like Africa is indeed in a nightmare , quite like that of the man in the story above and we probably are.

With a nightmare for our reality, what can we do? The answer to this is to wake up: wake up and build the same structures that we have seen in Western and Eastern countries, set our priorities right, and cease our utter dependence on the expensive goodwill of others. We should wake up and stop having such low bars and standards for our leaders. For once, we should see the value of electing someone for what s/he has done in the past, his/her record, the values their lives demonstrate, and the promise they hold. This instead of the emotions they whip, their parties, tribes, or bribes. We should take this pandemic as our wake-up call to prioritize, build and sustain effective, responsible and accessible healthcare systems, entrench good visionary leadership as our standard, and position ourselves to provide global solutions. Don’t we breathe same air? Don’t we argue that Africans are non-inferior and in some cases more blessed as compared to human beings from other areas? We should begin to manufacture most of what we need, strengthen research bodies in each country and be the centre for innovative concepts. We should take this season as constructive criticism in relation to what we have not done, and go ahead to do them.

Fellow Africans, we may demand respect from others on the basis of being as human as any other. However, the surest way is to earn it. Let’s rebuild our society, manufacture, produce and go back to a time when common good outdid selfishness all day everyday.

The one thing that would be a greater disaster than COVID-19 is to learn nothing from this crisis as continent and fail to wake up. It would be a tragedy if this pandemic doesn’t cause a shift in how we operate. If however we do wake up from our slumber, the even the sky will not limit Africa, my motherland, the cradle of mankind. By God’s grace!

As always, you have my permission to copy, print and publish, provided you clearly cite the source.

Please follow and like us: