None of her primary contacts have tested positive
The Covid-19 positive case in Gelephu on August 10 not only became the first positive case outside a quarantine facility, but also triggered a nationwide lockdown for the first time in the country.
The case of the 27- year-old woman also raised several questions on the testing mechanism based on the current understanding of the mechanism.
The woman had tested five times negative on the RT-PCR test, the confirmatory test for Covid-19.
Medical technologist and a member of the technical advisory group (TAG) of the health ministry, Rixin Jamtsho said that the woman could have been exposed to the virus in the past and had recovered.
This he said was because the woman tested positive for IgG antibody on three occasions, which is representative of a past infection. “And the positive result on the PCR test (test number six) could have been due to the shedding of the dead virus particles.”
He said there are several literatures that show RT-PCR results can test positive even for a dead virus. A PCR test, he said, amplifies the genetic materials exponentially by making exact copies of the molecule. “The copies produced are then used to compare with the gene of the virus. The sample here can be dead or alive.”
Rixin Jamtsho said that the evidence of the index case shedding dead virus could be deduced from her primary contacts. “None of her primary contacts have tested positive. If she was shedding live virus, she would have infected at least one of her close contacts.”
He explained that the initial results on PCR for the woman could have been negative because the virus had not reached the upper respiratory tract from where the swab for test is collected.
“If there are no viruses in the swab collected for the test, the test would not detect the virus. PCR might not be a sensitive method but it is a highly specific test, meaning even if the sample contains a small fraction of the virus, the result would be definitely positive.”
While there are very little chances of error in the sample collection, he said even if the samples were incorrectly collected, by now at least some of her close contacts should have tested positive.
This means that the woman did not have active infection, which is why she did not test positive on the PCR during the initial tests. The test picked up the virus (dead) during the sixth PCR test.
Who can spread the virus?
The woman in Gelephu continues to be asymptomatic and all the 135 primary contacts have tested negative to the virus.
However, the 25-year-old man who tested positive from the mini dry port in Phuentsholing was symptomatic when he was taken to the hospital on August 11. 15 of his primary contacts have also tested positive so far.
Rixin Jamtsho said that in the initial days of the pandemic, it was assumed that infected persons who are asymptomatic did not spread the virus. “But today there are many literature that say asymptomatic cases play an equal role in spreading the virus.”
He said that irrespective of symptoms, if an individual is infected he or she could infect others. “But the degree of transmission would be more for symptomatic patients because they cough and sneeze more than the one who do not have symptoms.”
The medical technologist said having a healthy body helps in fighting any sort of disease including Covid-19. “We have 100 people who have recovered from the disease so far without any specific medication,” he said. “If we can keep our body strong by eating healthy, our immune system can fight this virus on its own.”
However, he added that for now there is no evidence that the body develops long-term immunity against Covid-19. “But the body instantly fights the virus by producing antibodies as it enters our body. Which is why we must eat healthy and keep the body strong enough for it to fight any disease.”
Rixin Jamtsho said that there are scientific literatures that show about two to six percent of the people developing symptoms for Covid-19 after 21 days.
“We have released more than a thousand people from the quarantine centres following the most stringent protocols. But studies outside has shown that there are people who become positive after 21 days of contracting the infection.”
Because of this, he said that the second layer of surveillance was put in place. Under this, a person completing the mandatory 21-day quarantine is asked to stay home, minimise contact with others and immediately report to authorities if any flu-like symptoms appear.
“However, it seems many don’t take this advice seriously. Considering the threat and the 2-4 percent chance, we need to strictly enforce this again and make people aware of the danger if they don’t follow the rules.”
Meanwhile the government’s decision to extend the quarantine period from 14 days to 21days was because the probability for a 14-day incubation period was between 10-12 percent as compared to 2-6 percent for 21 days.