Months after developing COVID-19, many people continue to suffer debilitating symptoms such as fatigue, gastrointestinal problems, depression and “brain fog,” sometimes appearing long after infections subside and affecting even those who only experienced mild bouts of the disease.
The condition, commonly referred to as “long COVID-19,” has mostly been studied in adults, yet it continues to be an enigma to the many doctors and scientists studying patient cases.
Even more of a mystery is how common the condition is in children infected with the virus, and how it manifests in their bodies. There’s no test to confirm long COVID-19, and younger kids may not be able to explain what they’re feeling, challenging doctors’ efforts to diagnose them properly.
It’s a puzzle that has become more worrisome now that a new school year is on the horizon, as coronavirus cases surge across the nation — mostly among the young and unvaccinated — and as those under 12 years old remain left out of COVID-19 vaccination eligibility.
Now, a new analysis of data of nearly 7,000 kids who tested positive for COVID-19 and experienced symptoms, part of the U.K.’s ZOE COVID Symptom Study, may quell some parents’ fears.
Less than one in 20 children (4.4%) felt coronavirus symptoms for more than four weeks, while just one in 50 (1.8%) experienced symptoms for more than eight weeks, according to the study published Tuesday in The Lancet Child & Adolescent Health. Nearly all children made a full recovery.
Sickness lasted five days, on average, in kids between 5 and 11 years old and seven days in kids aged 12 to 17. The most common symptoms reported were headaches, fatigue, sore throat and loss of smell; kids in the study didn’t experience serious neurological symptoms felt by some adult long-haulers such as seizures, anxiety or trouble concentrating.
In comparison, the same study found that about one in seven adults experienced COVID-19 symptoms for more than four weeks.
“We know from other studies that many children who catch coronavirus don’t show any symptoms at all; and it will be reassuring for families to know that those children who do fall ill with COVID-19 are unlikely to suffer prolonged effects,” study senior author Emma Duncan, a professor of clinical endocrinology at King’s College London, said in a statement. “However, our research confirms that a small number do have a long illness duration with COVID-19, though these children too usually recover with time.”
Nearly 4.2 million children have contracted the coronavirus as of July 29, the American Academy of Pediatrics calculates. In the last week, about 72,000 cases in kids were reported, a “substantial increase” from the prior week when about 39,000 cases were added.
Children represent 14.3% of total coronavirus cases in the country, but for the week ending July 29, children made up 19% of reported weekly cases.
“That’s high and considering the fact that we are vaccinated now, what that’s telling us is that unvaccinated people are getting infected in higher numbers because the virus is more infectious with the delta variant,” Dr. Yvonne Maldonado, chief of the division of infectious diseases in the department of pediatrics at Stanford Medicine, told CNN. “Our sense is because kids can’t get vaccinated, parents should clearly be vaccinated themselves, and if their kids are 12 and older they should be vaccinated, as well.”
It appears children are still safe from severe COVID-19, even when infected with the more dangerous delta variant. “However, there is an urgent need to collect more data on longer-term impacts of the pandemic on children, including ways the virus may harm the long-term physical health of infected children, as well as its emotional and mental health effects,” the pediatric group said.
Other studies paint a more worrisome picture
Some studies, on the other hand, have found more worrying trends in kids regarding long COVID-19.
Among about 100 infected children in Italy, 42% had at least one coronavirus symptom two months after testing positive, one April study found. After four months, the number fell to 27%.
A U.K. non-peer reviewed study of nearly 4,700 children estimated that 4.6% of those who had been infected with the coronavirus had lingering symptoms for more than four weeks. Girls, teenagers and kids with chronic health conditions experienced higher rates of long COVID-19.
More research from Russia found that a quarter of kids had persistent symptoms months after being released from a hospital for COVID-19, with older age and allergic diseases raising risks for long COVID-19.
What causes long COVID-19 in kids?
Experts are still trying to figure out why adults are left suffering with symptoms for months after initial diagnosis, but they say biological differences between children and adults make it that much more difficult to find the cause in kids.
For example, some adults with long COVID-19 have noticeable physical changes in their heart or blood clots showing up on their CT scans, Dr. Alicia Johnston, head of the Boston Children’s Hospital long COVID clinic, told STAT. Meanwhile, kids “have normal white blood cell counts in general, normal inflammatory markers, normal pulmonary function tests, normal EKGs, normal X-rays, normal echocardiogram. And yet they’re clearly impaired.”
Dr. Akiko Iwasaki, an immunologist working on viral infectious diseases and vaccines at Yale University in Connecticut, proposed three potential mechanisms behind the condition in a March post in the blog Elemental.
One possibility is that long-haulers have “persistent viral reservoirs,” like a storage bin of coronavirus particles that continue to make its host sick. “Viral ghosts” — fragments of the virus such as its genetic information or proteins — could be separate culprits that are capable of “stimulating the immune system” even after infection is cleared, Iwasaki wrote.
Or, the coronavirus somehow convinces the body to turn on itself, causing it to aggressively attack its own defenses, as is the case with most autoimmune disorders, including lupus and rheumatoid arthritis.
“Many studies have provided support for all three of these mechanisms,” Iwasaki wrote. “I suspect that people with long Covid have varying degrees of all three mechanisms taking place. Thus, long Covid consists of multiple types of diseases.”