High virus in kids with Covid-19, but are they contagious?

Coronavirus disease (Covid-19) rarely sickens children, and when it does, it usually causes mild disease. But a new study indicates that infected children with mild and moderate disease carry as much virus as adults, sparking debate on whether they can potentially spread infection as easily as adults.

New research shows that infected children have as much coronavirus in their nose and throats as adults, with children younger with than five with mild symptoms having 100 times more virus than adults, according to results of tests that measured genetic material of the new coronavirus (Sars-CoV-2) in the nose and throat swabs of children with mild to moderate Covid-19.

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Sars-CoV-2 genetic material, or RNA, is not infective like the whole virus, but authors note there is a correlation between higher RNA load and ability to spread disease.

“Our study is limited to detection of viral nucleic acid, rather than infectious virus, although Sars-CoV-2 paediatric studies reported a correlation between higher nucleic acid levels and the ability to culture infectious virus,” said the study by researchers in Chicago and published in JAMA Pediatrics, a journal of the American Medical Association.

“Young children can potentially be important drivers of Sars-CoV-2 spread in the general population, as has been demonstrated with respiratory syncytial virus, where children with high viral loads are more likely to transmit. Behavioural habits of young children and close quarters in school and day care settings raise concern for Sars-CoV-2 amplification in this population as public health restrictions are eased,” said the study.

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The study has public health implications for opening schools and planning vaccination campaigns to include children once Covid-19 vaccination are available in 2021.

Children are established drivers of respiratory infections such as seasonal flu and the common cold, but data on whether children are less likely to spread the infection remains sparse.

Children and teenagers have half the risk of getting infected by Sars-CoV-2 as compared to adults, according to a large systematic review of at least 6,300 studies published in May in the preprint journal of medical sciences, medRxiv in May. The study is being peer-reviewed.

The review said there was weak evidence on the role of children and young people in transmission of Sars-CoV2 at a population level. “Our study provides no information on the infectivity of children,” said the study by researchers at University College London, which analysed data from 6,327 studies published till May 16 this year.

“The role of children and young people in spreading the disease depends on several factors, including their susceptibility to infection, severity of symptoms, viral load and social behaviour. We need far better understanding of the role of children in transmission as it has implications on school reopening and restoring some degree social normalcy,” said Dr Navin Dang, director and senior microbiologist at Dr Dang’s Lab, Delhi.

“We don’t have data from India yet as very few children have been tested, which means that symptoms and illness even in children exposed to infection within families has fortunately been rare. We don’t have a big enough sample size needed to quantify CT values in children, but it’s data worth analysing,” said Dr Dang.

CT stands for cycle thresholds, which are the number of cycles needed to amplify a virus’ RNA during a reverse transcription polymerase chain reaction (RT-PCR) test approved to diagnose Covid-19. The higher the viral load, the fewer cycles are needed to get a clear result.

Schools across India have been shut since March 21, the weekend before a national lockdown was announced by Prime Minister Narendra Modi on March 24, which has limited physical interaction between children, but with some relaxation of movement restrictions, social interaction is set to increase.

Studies on Covid-19 prevalence in children have produced widely varying results. Large studies from Iceland, the Netherlands and Spain and Italy showed markedly lower Sars-CoV2 prevalence among children and young people, but studies from Sweden, the UK and some areas in Switzerland and Germany found no difference in infection prevalence between adults and children.

“The JAMA study is particularly significant as you cannot expect very young children to wear masks properly or follow social distancing norms without supervision in crowded classrooms, canteens and playgrounds. This can led to infection clusters in schools, from where children can spread it to staff, families and communities or neighbours without developing severe disease themselves,” said Dr Rajesh Sagar, professor in the department of psychiatry, All India Institute of Medical Sciences Delhi.