Youngsters might carry the next SARS-CoV-2 viral load
In a comprehensive study, researchers reported that children carry higher SARS-CoV-2 viral loads and could potentially be more contagious even with asymptomatic treatment.
When the COVID-19 pandemic hit the world, a positive highlight was that the SARS-CoV2 virus apparently spared children. Compared to adults, it has been reported that fewer children are infected and need to be hospitalized because of the SARS-CoV2 virus. However, a study with 192 children showed that although children appear asymptomatic or suffer from mild symptoms, they have a high SARS-CoV-2 viral load. The high viral load means they can spread the infection to their family members and other people in close proximity.
The study included children who called in sick in emergency clinics or who were hospitalized for confirmed or suspected SARS-CoV2 infection. It also included children suffering from Multi-System Inflammatory Syndrome (MIS-C), an inflammatory disease that affects different parts of the body and is believed to be associated with COVID-19. The study was published in the Journal of Pediatrics.
Of the 192 children, 49 tested positive for SARS-CoV2, and another 18 children were diagnosed with MIS-C. While the study included children between the ages of 0 and 22 years, 34% or 16 children with SARS-CoV2 infection were between 11 and 16 years old. Children with MIS-C were younger with 39% or 7 children between the ages of 1 and 4 years.
Most of the children reported symptoms that were common with other illnesses such as influenza or the common cold. Children with or without SARS-CoV2 infection reported fever, cough, congestion, runny nose and headache. This can make diagnosis quite difficult based on symptoms alone. Loss of smell and sore throat were just a few characteristic symptoms of SARS-CoV2 infection.
The results of the nasal and throat swabs and blood samples from these children showed a high viral load in the early days of the infection. The viral load observed in these infected children was comparable to the viral load seen in adults who required intubation due to COVID-19. Even during the asymptomatic phase of infection, the viral load was higher in infected children than in hospitalized adults who showed symptoms for over a week. Dr. Lael Yonker, director of the MGH Systic Fibrosis Center and lead author of the study, said: “I was surprised at the high levels of virus we found in children of all ages, especially in the first two days after infection. I didn't expect the viral load to be this high. …, But the viral load of these hospitalized (adult) patients is significantly lower than that of a "healthy child" walking around with a high SARS-CoV2 viral load. "
In addition to the viral load, the researchers also examined the gene expression of the ACE2 receptor, which binds to the SARS-CoV2 virus. Their study found that while ACE2 expression was higher in infected children compared to uninfected children, there was no correlation between viral load and ACE2 expression. This suggests that children after infection may carry high viral loads regardless of ACE2 levels, suggesting that children, despite their own susceptibility to developing COVID-19, could be more contagious. Additionally, the researchers found that ACE2 expression levels increased with age, and high ACE2 levels could predispose some children to infection.
The researchers also found that in children with MIS-C, the immune response is accelerated and this can lead to complications, including heart failure. MIS-C is a multiple organ infection that can develop in children with COVID-19 for several weeks after infection. Dr. Fasano explains, “This (MIS-C) is a serious complication resulting from the immune response to COVID-19 infection and the number of these patients is growing. And like with adults … the heart seems to be the favorite organ targeted by the immune response after COVID-19. "
More than a quarter (27%, or 3 in 11) of asymptomatic children suspected of being exposed to the virus tested positive. Of the infected children, nine children had no known exposure to the virus. Half of the children with acute infection attended elementary school.
These results have implications for the reopening of schools and daycare centers where children are in close contact with other children and adults such as teachers. Dr. Alessio Fasano, Director of the Research Center for Mucosal Immunology and Biology at MGH and senior author of the paper, stated: “During this COVID-19 pandemic, we were mainly studying symptomatic subjects, so we came to the wrong conclusion that the vast majority of those infected are adults. However, our results show that children are not protected against this virus. We shouldn't rule out children as potential spreaders for this virus. "
Given that a significantly larger number of children (51% or 25 children) with SARS-CoV2 infection came from lower-income households, this is especially important for the families of these children, who are most likely to live in multi-generational households which increases the risk of infecting vulnerable older adults such as their grandparents.
The effects of having children as carriers of infections are severe. The authors of this study make various recommendations to ensure the safe reopening of schools and other centers. They believe that continuous and routine screening of all students regardless of the presence of symptoms, and reporting of these results in a timely manner, is critical to the safe return of students to schools. In addition, social distancing, effective hand washing, universal mask use, and a combination of distance and face-to-face learning are essential and prudent methods of combating the spread of SARS-CoV2 infection.
Written by Bhavana Achary, PhD
References:
Original study – Yonker LM, Neilan AM, Bartsch Y, et al. Pediatric SARS-CoV-2: Clinical Presentation, Infectivity and Immune Responses (published online before going to press, August 18, 2020). J Pediatr. 2020; S0022-3476 (20) 31023-4. doi: 10.1016 / j.jpeds.2020.08.037 https://www.jpeds.com/article/S0022-3476(20)31023-4/fulltext#secsectitle0025
Press release: https://www.eurekalert.org/pub_releases/2020-08/mgh-rsc081720.php
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