As parents we worry a lot about our children’s health and most especially now, with this new coronavirus (SARS-Cov-2). With so much information currently available online about COVID-19 it can become difficult for us to sift through the real from the fake news. I hope to simplify things a little in this post and share some of the more convincing theories we have on COVID-19 in children.
Whilst children can become infected with the virus, in most cases they are asymptomatic or only present with mild disease. This has been found to be the case with some other viruses such as chickenpox, which affects the older generation more aggresively. However, it is more common for viruses to affect both the very young and the very old more severely. The immune system seems to be really important here and this is one of the main responses researchers are looking at to better understand the progression of COVID-19 in children.
AGEING AND THE IMMUNE RESPONSE
The immune system is supposed to remove pathogens from the body without causing too much damage to healthy cells. This is important because a too vigorous response can end up damaging healthy cells as well. This is what we see in COVID-19 where the most serious complication is SARS (severe acute respiratory syndrome). The pathogenesis of SARS is complex, but the immune system’s response to the virus seems to be a very important contributor. It is responsible for much of the damage to the lungs.
The immune system is made up of an innate and adaptive immune response. The innate response is the body’s nonspecific defense mechanisms that kick in straight away when presented with a foreign pathogen. If the innate response is unsuccessful at destroying the pathogen, the adaptive response starts a few days later. This is a more specific targeted response involving the B and T cells.
Our immune system becomes weaker and less efficient with age and chronic diseases also weaken the immune system, making it harder to fight off infection. As we age our innate immunity is slower to respond, but in the elderly once this innate immunity eventually gets going it is often overzealous as it tries to catch up. The T-cell responses are also weaker with age making it more difficult for the immune system to actually get rid of foreign pathogens.
It has also been suggested that since a child’s immune system is still developing they are unable to mount a very severe immune response, which protects the lungs from the immune mediated damage. A contrasting theory however, is that a child’s immune system is more efficient than an adults. Children are able to develop very high fevers that you often don’t see in adults. A fever is an important physiological response, which allows certain immune cells to work better. It is suggested that children’s immune systems are therefore more able to confine the virus to the upper airways long enough to be able to destroy it.
THE SARS-COV-2 RECEPTOR
Another theory involves the ACE2 receptor. The SARS-CoV-2 virus gains entry into human cells by binding to these receptors on our cells. These receptors are found throughout the body but are in higher concentrations in the respiratory tract, which can explain how the virus gains entry into the body. It has been hypothesized that children’s ACE2 receptors are not as developed as adults and are in lower concentrations in the lungs when compared to the upper airways. This could explain why most children present with mild disease and mainly symptoms of an upper respiratory tract infection.
WHAT DO WE KNOW?
At this point we don’t know a great deal. This virus is still very new and research is limited. Based on the current available evidence, children do not seem to be at any higher risk for COVID-19 compared to adults. Initially, it was actually thought that children were not getting infected as much or even at all. This was only because they were not presenting with severe enough symptoms to get tested.
Initially it was thought that children were getting infected at the same rate as adults and were therefore contributing to the spread of the disease as ‘silent’ spreaders. Recent evidence has however found that children under 18 years of age don’t really pass on the virus. For reasons not yet completely understood, most children don’t seem to get very sick from SARS-CoV-2 and this may have something to do with their viral loads. It is now being suggested that children are not very infectious because they do not have very high viral loads.
It has however been shown that some infants can develop more severe illness compared to older children. This is possibly because an infant’s immune system is very immature and a mother would also not have developed any (or enough) antibodies to pass on in-utero since this virus is still so new.
Unfortunately much more time and research is needed to fully understand COVID-19 in children. Until then we cannot assume our children will escape this virus. We still need to protect them and make sure they practice good respiratory and hand hygiene and maintain a social distance.