1st Case 23 yr old Sailor from Italy.
The lab results from ESR NZ indicate that SAMOA’s first case was previously infected with covid19 disease and has been recovered. This statement is verified by a thorough assessment based on the results of further testing using blood, as well as the clinical observations.
Explanation of the positive PCR result from sample of right nostril and negative result from left nostril (test using the nasal swab): The PCR testing platform generally aims to detect or pick up the virus-remains (genetic material) present in a body site, but cannot tell us whether the remains are from a dead or a live virus. The different results from samples of the two nostrils can say that the virus-remains is not readily present in the nasopharynx or nose of this person as it was only picked up by the samples collected through the right nostril. If it was present in high amounts that are considered contagious/infectious, it would have been picked up by swabs collected through the left nostril as well.
Further clarifications: The analysis of the positive result by all PCR technologies in three different laboratories, shows that the virus-remains being picked up by these methods and hence instigated the positive result is only present in insignificant low amounts. This is consistent with having a negative result of all the samples from the left nostril, which can say that the virus-remains is either present in very low amounts, or no longer present at all. This analysis concludes that this is only a case of past infection that should not be considered infectious and is incapable of spreading. Therefore, the lab advises that if the case remains asymptomatic and clinically well after 10 days from first detection of the positive (18/11/20), the case should be considered non-infectious and be discharged from isolation.
We also advise that regardless of the test result, individuals should continue to follow Public Health guidelines including social distancing and wearing masks in public places, to reduce the risk of transmission and infection.
Overall and after a careful analysis of both molecular and serological test results, this case most likely had a historic infection with residual excretion of RNA (i.e. dead virus) as seen in many covid19 patients and his intermittent viral RNA excretion may carry on for months after the original infection (ref: peer-reviewed studies). This case is noted to have had a previous Covid 19 positive result in June 2020 in Italy .
Besides considering that the host is asymptomatic and does not fit the clinical criteria of being a firm covid19 case, the infectivity status of the host based on clinical assessment + analysis of lab results (positive with very low viral load [Ct values = 34, 37] and negative on collections from the left nostril), is considered very low. Moreover, laboratory test results should always be considered in the context of clinical observations and epidemiological data in making patient management decisions. Table 2 shows the blood sample results. His serology shows a strong positive.
Therefore, the case has evidence of low-level RNA excretion which, with his high antibody titre, would better fit with a historic infection with intermittent RNA excretion than a recent infection
2nd Case : 70 yr old Samoan male
The lab results from ESR NZ indicate that the second case was previously infected with covid19 disease, but has fully recovered. This statement is verified by a thorough assessment based on the results of further testing using blood, as well as the clinical observations.
Explanation of the positive PCR result from Samoa and Negative PCR result from ESR NZ (test using the nasal swab): The PCR testing platform generally aims to detect or pick up the virus-remains (genetic material) present in a body site, but cannot tell us whether the remains are from a dead or a live virus. The dissimilar results from the two labs can only say that the technologies used can detect the virus-remains at different extents or levels. This usually occurs in situations where the virus-remains is present in very low amounts that will make it hard for some PCR machines to pick up. That said, the machine (GeneXpert) used by most Pacific island countries including Samoa is able to pick up the virus even if a very low amount is present in a site (nasopharynx/nose in this case). This also tells us that the machine we use is very reliable in the sense that we should never miss a positive case.
Further clarifications: The analysis of the positive result by GeneXpert shows that the virus-remains being picked up by this method and hence instigated the positive result is only present in very low amounts. This is consistent with having a negative result of the same sample when tested at ESR NZ, as very low amounts can either be detected or undetectable depending on how different PCR machines work. This is also backed by obtaining negative results (GeneXpert) from two other samples collected on the same night, which were also tested negative at ESR lab, which can say that the virus-remains is either present in very low amounts, or no longer present at all. This analysis concludes that this is only a case of past infection that should not be considered infectious and is incapable of spreading.
Therefore, depending on the clinical picture,if the case remains asymptomatic and clinically well after ten days from first detection of the positive (26/11/20), the case should be considered non-infectious and can be discharged from isolation.It is also advisable that regardless of the test results, individuals should continue to follow Public Health guidelines including social distancing and wearing masks in public places for general precautions.
Leausa Samau Dr Take Naseri.
DG/CEO MoH
