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What is COVID-19?
Coronaviruses are a large family of viruses found mostly in animals. In humans, they can cause mild to moderate respiratory illnesses ranging from the common cold to more severe diseases such as Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome. The new disease, caused by the SARS coronavirus 2 (SARS-CoV-2), has been named COVID-19.
While many of the characteristics of COVID-19 are still unknown, mild to severe symptoms have been reported for confirmed cases. Symptoms in children are similar to those in adults, namely fever, dry cough, and fatigue, with some also experiencing abdominal pain and diarrhea.
What do we know about COVID-19 and how it impacts children?
A recent study published in the journal Pediatrics, looked at the COVID-19 transmission patterns of 2143 infected children (less than 18 years of age) living in China from January 16th to February 8th of this year. The study found that over 90% of the infected children had either no sypmtoms, or symptoms that were mild to moderate — as opposed to severe or critical. That means that even if the children were sick, 90% did not have trouble breathing, need oxygen, or need to be in the intensive care unit.
Although most infected children experienced mild symptoms, younger children were more vulnerable to severe COVID-19 symptoms than older children (10.6%, 7.3%, 4.2%, 4.1% and 3.0% for children <1 year old, 1-5, 6-10, 11-15 and ≥16 years, respectively).
Interestingly, in adults, only 80% had mild to moderate symptoms. So it seems that, compared to children, adults are more vulnerable to severe COVID-19 symptoms.
So why is COVID-19 milder in children compared to adults?
We're not sure yet, but Dr. Petter Brodin, a member of the Social Exposome Research Cluster, is working on understanding why the virus is affecting different groups of people.
An editorial written by Dr. Brodin suggests that the presence of other viruses in the mucosa of lungs and airways, which are common in young children, could limit the growth of COVID-19 by direct virus-to-virus interactions and competition. This theory fits with emerging data from the current pandemic, which has indicated a link between the number of viruses and COVID-19 severity.
Another theory suggests that therapies used to treat adults with hypertension, which is much less common in children, may induce the expression of a receptor that COVID-19 binds to.
Researchers don’t yet have a good handle on which of these theories—if any—explain the apparent resilience that children have to COVID-19. Further studies will be required to test these hypotheses, but it is clear that understanding COVID-19 symptoms in children will provide important information about the disease.