The Omicron strain of Covid "acts differently" in children and there is one key symptom parents should watch out for.
Dr Andrew Pavia, a paediatrician and expert in infectious diseases in childhood, believes the mutation presents differently when youngsters are involved.
The variant - which first emerged in the UK last November - was recently proven to be milder than its predecessor Delta and the original Covid-19 strain.
But this mildness is reportedly most noticeable in patients who have already been vaccinated.
Most children have not been vaccinated, which experts believe has opened a route for Omicron's mutations to hit them harder.
Dr Andrew, who works at Primary Children’s Hospital in Utah, said: "There is reason to think that acts differently in younger children.
"We are seeing the shift towards more disease in younger children; that probably has to do with changes in the virus."
Dr Andrew says Omicron seems to attack the "upper airways" to a greater extent than the lungs, reports The Sun.
And because younger children "have smaller airways", it affects them differently.
The doctor said the children who became unwell enough with Omicron to need hospital care often presented with a specific cough - that sounds like a dog's bark, he said.
This type of cough, described as "croup-like" by medics, is not thought to be harmful to the kids.
But it is still unpleasant for parents hearing the harsh sound, which can naturally increase their concerns.
The sinuses of children are smaller than adults, and can become blocked easily, and in turn cause inflammation that can spark a harsh cough.
A common cold infection experienced as mild by an adult, could cause more problems for a child.
When Omicron settles and causes inflammation in the upper airway, infected children will present a cough that seems more severe and may even need breathing assistance, Dr Andrew said.
Omicron also infects patients in a different way to the previous strains - which dived deeper into the lungs where it could cause more life-threatening illness.
At the end of last year, experts shared a list of the specific Omicron symptoms parents should watch out for in children.
Symptoms of Omicron in childhood:
- Fever
- Runny nose
- Croup - a 'barking' cough
- A more usual sounding cough
- Rashes
