The World Health Organization (WHO) has released a new definition for post COVID-19 condition, commonly known as long COVID, in children and teenagers.

In a document released Thursday, WHO officials say it started to come up with a specific definition for long COVID in children and teens because the virus affects them differently than adults.

According to the new definition, children and teens with long COVID are more likely to have fatigue, an altered sense of smell (anosmia), and anxiety than healthy children.

The WHO added that children, teenagers, and adults all experience symptoms of long COVID within three months of being infected, and symptoms last for at least two months once they start.

“Symptoms generally have an impact on everyday functioning such as changes in eating habits, physical activity, behaviour, academic performance, social functions (interactions with friends, peers, family) and developmental milestones. Symptoms may be new onset following initial recovery from an acute COVID-19 episode or persist from the initial illness. They may also fluctuate or relapse over time. Workup may reveal additional diagnoses, but this does not exclude the diagnosis of post COVID-19 condition.”

Their findings suggest anyone aged 19 or younger is not as likely to show symptoms or become severely sick after getting COVID-19, and may show no symptoms at all.

While the WHO released its definition for long COVID in adults in October 2021, the latest definition of long COVID was created using what the WHO refers to as a “Delphi exercise,” which involves repeatedly surveying experts and patients.

Anyone who has been infected with COVID-19 -- no matter how severely -- can suffer from long COVID according to the WHO, though it’s more common in people who had serious illness.

The Institute for Health Metrics and Evaluation estimated 145 million people suffered from long COVID by the end of 2021, with 22 million people showing persistent symptoms 12 months after they became infected by virus.

The WHO says there is still limited information about long COVID in children and teenagers, and the new definition will “contribute to a global understanding of its prevalence and allow for more comparable research studies.”