Discharging of COVID-19 positive patients

According to the current revised guidelines in Malawi, being implemented since 2nd July 2020, one can be discharged from quarantine, isolation, hospital and declared "recovered" even if their COVID-19 status is still POSITIVE. 

According to a memo Ref no. CD/101 signed by Chief of Health Services Dr Charles Mwansambo, there are SIX criteria listed on discharging both symptomatic and asymptomatic patients and contacts. In this article I won't go into details of each conditions, I will only dwell much on condition number 1 criteria (b) which I find more relevant on elaborating more on how and why discharging positive cases. 

Condition 1 says (paraphrased). A symptomatic patient can be discharged after 10 days from onset of symptoms plus at least 3 days without symptoms (fever and respiratory symptoms) so long as (a) their test result on 14th day is NEGATIVE or (b) their test result on 14th day is POSITIVE but their cycle threshold (Ct) value is greater than 30. 

Now what is cycle of threshold value? I will try to explain in least diagnostic/medical terms as possible. Imagine you have a dam with 50 chambo fish and maybe some usipa and you are instructed to fish out all the chambo one by one, all factors constant, how long would it take you to catch the 1st, the 25th and the 50th chambo respectively? Is there a chance you may catch an usipa? I hope we all agree that the last chambo would take forever to catch than the first and of course it maybe inevitable to catch an usipa at some point.

Similarly, during testing (in this case for COVID-19 using a gold standard method called polymerase chain reaction-PCR), a positive sample has a number of viruses, medically commonly known as viral load/copies. The number of viral copies may range from hundreds to millions. Imagine these viruses are the chambo and the sample is the dam, at first catch (by the machine) it will be very easy to find the viruses in the sample but as time goes because they are being 'fished out', by and by it will be hard for the machine to find them. Let's say Ct value is when you have successfully fished out a chambo, in testing let's say it's when we have successfully detected in medical language we also use the word amplified. 

So first catch is the first completed cycle. Threshold is just more of a level, if you successfully catch the chambo and not usipa then you have completed/you are above the chambo catching level hence we may call it first chambo cycle threshold so on and so forth, by the time we will reach 30th cycle we may even be tired and give up because it will be very hard to find that chambo in the dam, similarly the machine reaches a time later on where it can no longer detect/amplify the viral copies simply because there are now scarce in the sample. At times you may catch the usipa instead of the chambo, but because you were instructed to catch chambo only then the usipa caught won't be counted as a complete cycle, similarly during testing we call it background noise where you may detect something not in your interest, it may look like a chambo catch but in reality it's an usipa catch hence it won't be counted as a complete cycle threshold. 

So for any disease usually the more pathogens (viruses, bacteria, parasites etc) you have, the easier you can share or transmit from you to another person. Medically we call this person a highly infectious individual and this usually happens when one is newly infected, as time goes by the pathogens tend to decrease in number hence the infectiousness of that person also drops. Similarly patients with COVID-19 high viral load (less Ct value) are considered highly infectious than patients with low viral load (high Ct values) who are considered less infectious. 

In conclusion, more viruses in a sample the sooner the cycle threshold is detected and also reflects the recency of the infection, similarly the less the viruses in the sample the later the cycle threshold value and also reflects how formerly an infection is. In short if your Ct value is less than 30, it means you still have more viruses and you are likely to infect others while if you have greater than 30 Ct values, it means you have less viruses and you may hardly infect others, hence in both cases the machine is likely to detect both samples as positives but one can qualify to be discharged and one not.