SHILLONG: What is the required period for quarantine for different categories of people tested? Who is a primary source? Who is a secondary source? What is the quarantine period respectively? To get clear answers The Shillong Times spoke to a senior medical practitioner of long standing with experience in public health.
He said a primary source is one who has had direct contact with a COVID-19 patient. It could be a doctor, nurse, ward boy or family member that have not used personal protective equipment (PPE) while treating a patient.
Such people should be under mandatory supervised quarantine for 28 days because they fall under the high-risk category.
Those that have used PPE and, therefore, their exposure is lower are in the low-risk category and should be under home quarantine for 14 days if no symptoms develop.
“COVID-19 has an incubation period of 5-6 days hence within 11-12 days the symptoms will definitely show. But there are always outliers that do not develop the classic symptoms, “ the doctor remarked
He explained that a secondary source is one who has not come in contact with a COVID-19 patient but has only been in contact with others who have been in contact with the primary source. For them a home quarantine period of 14 days is enough. He further clarified that there is no such thing as a 7-day quarantine period, saying it is either 14 or 28 days.
About antibody tests which will determine whether a person had suffered from COVID-19 but without the severity that others experience, the doctor says, “There are two types of antibody tests – IgM and IgG. The antibodies usually appear within 5-7 days of the onset of COVID-19.
These are serological immunoassays that detect viral-specific antibodies (IgM and IgG) or antigens.
IgG/IgM serological tests offer some advantages over RT-qPCR tests that rely on nasal swabs. Firstly, serological tests detect human antibodies (proteins belonging to the immunoglobulin class) which are known to be much more stable than viral RNA. As a result, IgM/IgG serological specimens are less sensitive to spoilage during collection, transport, storage and testing than RT-qPCR specimens.
Secondly, because antibodies are typically uniformly distributed in the blood, serological specimens have much less variations than nasopharyngeal viral RNA specimens and can be easily collected with minor discomfort to the patient.
Thirdly, unlike RT-qPCR, serological tests can detect past infection because virus-specific antibodies (unlike viral RNA) can persist in the blood for several weeks/months after onset of symptoms.
However, IgM/IgG serological tests also have some limitations, mainly related to the slow pace of the human antibody response to SARS-CoV-2 (COVID-19). Although, several studies are still ongoing, SARS-CoV-2 antibodies may not be detectable before three days after onset of symptoms (or at least 7 to 10 days after infection).
While IgM/IgG serological tests alone may not be enough to diagnose COVID-19, they can be a valuable diagnostic tool when combined with RT-qPCR. In addition, because of their scalability, serological assays can be used in large-scale, whole-population testing to assess the overall immune response to the virus and identify asymptomatic carriers of the virus.
“Indeed, 20-80 per cent of COVID-19 cases are estimated to be asymptomatic,” the doctor remarked.
Speaking about home quarantine, the doctor said home quarantine ought to be strictly enforced and community surveillance is the best way forward.
“COVID-19 is not just a health problem to be fought by doctors and health workers only or by the administration. It is a community problem and hence has to be fought at the level of the community. If we slacken vigilance at this point it could very well lead to a community spread with so many people returning from what are red and orange zones across the country.”