Children are less commonly infected by Covid-19. When infected, they are less symptomatic and the development of the disease in their systems are less severe than adults infected with Covid-19. Symptoms, if present, are also nonspecific and resemble other non-Covid respiratory viruses, which creates a diagnostic dilemma.
The factors that are related to lower rates of SARS-CoV-2 infection (the virus that causes Covid-19) is related to less gene expression in the nasal epithelium. Scientifically speaking, the nasal epithelium is one of the first sites of infection with SARS-CoV-2, where the angiotensin-converting enzyme 2 (or ACE2), a protein/enzyme found on the surface of many cells, binds with the SARS-CoV-2 spike protein. According to experts writing in The Conversation, this binding, prior to entry and infection of cells, is like "a key being inserted into a lock", where ACE2 acts as "a cellular doorway" or "receptor" for the virus that causes Covid-19.
Fortunately, this ACE2 expression is less in children less than 10 years of age and therefore, children are less affected than adults. However, once infected, a child can carry high levels of the virus in their upper airway, particularly early on in the development of acute SARS-CoV-2 (first two days of symptoms), compared with adult patients with severe Covid-19 infection. Yet, children display relatively mild or no symptoms.
What is more important is that although ACE2 expression increases the susceptibility of infection, once infected a child can carry a high viral load, regardless of ACE2 expression. There is no age correlation in children to the viral load, indicating that infants through young adults can have a high load of the virus, which is the major concern when thinking about opening schools and daycare centres.
Fallacies in diagnostic tests of severe Covid-19 in children
Although most paediatric Covid-19 patients are less symptomatic and less severe, a subset of them develop a severe disease called the Multi-system Inflammatory Syndrome in Children (MIS-C). This can include having fever, the involvement of at least two organs, hypotension (low blood pressure), and cardiac involvement requiring aggressive therapeutic interventions such as intravenous immunoglobulin (IVIG), steroids, oxygen supplements, fluid resuscitation, empiric antibiotics etc. The disease is also associated with hyper inflammatory markers and SARS-CoV-2 antibodies. MIS-C is a post-infectious immune dysregularity disorder and clinical symptoms are observed a few weeks after SARS-CoV-2 infection. When symptoms appear, the RT-PCR test for SARS-CoV-2 usually comes as negative. Not infrequently, patients and their caretakers also cannot recall exposure to Covid-19, resulting in diagnostic dilemmas.
However, it is crucial to diagnose Covid-19 in order to isolate affected children and for optimum clinical management. Under these conditions, antibody tests for SARS-CoV-2 has diagnostic value, even though it is primarily used for serosurvelliance and concerned authorities in Bangladesh are planning to approve its use, provided it is not used for diagnostic purposes. The antibody test usually becomes positive two weeks after infection.
For more specific serodiagnosis, the serum IgM antibody of the receptor binding domain (RBD) of the SARS-CoV-2 spike protein is important, the testing of which is conducted in specialist laboratories. A positive test with IgM antibodies strongly suggests SARS-CoV-2 infection in symptomatic patients, according to an article in The Lancet from July 2020. While IgG antibodies also last long, they are nonspecific as they cross-react with other coronavirus IgG antibodies. In the absence of sophisticated antibody tests, a simple rapid antibody test can be used, which is easy to perform, requires a few drops of blood from the fingertip to be placed on the test strip with no processing, and the results are obtained within 15 to 20 minutes.
From an infection control perspective, it is crucial to identify the infected children early on for quarantine purposes, as up to one-third of school age children presenting with illnesses during the height of the pandemic were found to have SARS-CoV-2 infections. Children with mild symptoms of SARS-CoV-2 but with a high viral load in their upper respiratory tract usually present with nonspecific symptoms and overlap considerably with non-Covid respiratory related illnesses. Identifying SARS-CoV-2 infection will be more challenging during the coming winter season when increased aeroallergens and respiratory viruses, including RSV (causing bronchiolitis) and influenza, will be high.
Limiting the spread of SARS-CoV-2 infection in children is of particular concern when schools plan to reopen and the end of the pandemic is not quite in sight. It is also a matter of concern that children have not been going to school for about six months. We should weigh the balance of safety and wellbeing of the children, communities, and the families and households of these children, against the learning loss from prolonged absenteeism from school.
Once schools are reopened, infected children with mild nonspecific symptoms but with high viral load can spread the disease to their peers in the classroom and to school staff, as well as in the community during transport to and from school. Children being infected by their peers from school can carry the virus into their homes, exposing adults who are at higher risk of developing severe disease. The risk is higher in low income communities where household size is often larger with multigenerational cohabitants, which include the grandparents of the children.
What precautions should be taken if schools reopen?
The Ministry of Primary and Mass Education is planning to reopen schools, and has prepared preventive health guidelines to be followed in schools and has advised the Directorate of Primary Education accordingly. Depending on symptoms, including temperature monitoring, to identify SARS-CoV-2 infection will be unreliable as children have nonspecific symptoms and up to 50 percent of infected children do not have fever. Instead, infection control measures should minimise the possibility of viral spread. We should focus on a strategy that includes compulsory use of face masks, social distancing, hand washing, maintenance of respiratory hygiene and/or remote learning. If possible, all students should be screened for SARS-CoV-2 infection and routine screening protocols should be established. If school authorities don't take necessary precautions and follow the aforementioned steps, it is likely that children unwittingly may cause an increase in infections in the community.
Professor Md Salim Shakur PhD is Senior Consultant at the Department of Paediatrics at United Hospital Ltd.