High virus load in children, but does that raise spread risk?

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, sparkingdebateonwhetherthey 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 youngerwiththanfivewithmild symptomshaving100timesmore virus than adults, according to results of tests that measured genetic material of the new coronavirus (Sars-cov-2) in the nose andthroatswabsofchildrenwith mild to moderate Covid-19.

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 highernucleicacidlevelsandthe ability to culture infectious virus,” said the study by researchers in Chicago and publishedinjamapediatrics,ajournal of the American Medical Association.

“Young children can potentially be important drivers of Sars-cov-2spreadinthegeneral population, as has been demonstrated with respiratory syncytial virus, where children with highviralloadsaremorelikelyto transmit. Behavioural habits of young children and close quarters in school and day care settings raise concern for Sarscov-2amplificationinthispopulation as public health restrictions are eased,” said the study.

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

Childrenareestablisheddriversofrespiratoryinfectionssuch 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 halftheriskofgettinginfectedby Sars-cov-2 as compared to adults, according to a large systematic review of at least 6,300 studies published in May in the preprintjournalofmedicalsciences,medrxivinmay.thestudyis being peer-reviewed.

The review said there was weakevidenceontheroleofchildren and young people in transmissionofsars-cov2atapopulationlevel.“ourstudyprovidesno information on the infectivity of children,” said the study by researchersatuniversitycollege London, which analysed data from 6,327 studies published till May 16 this year.

“The role of children and youngpeopleinspreadingthedisease depends on several factors, including their susceptibility to infection, severity of symptoms, viral load and social behaviour. Weneedfarbetterunderstanding oftheroleofchildrenintransmission as it has implications on school reopening and restoring some degree social normalcy,” saiddrnavindang,directorand senior microbiologist at Dr Dang’s Lab, Delhi.

“Wedon’thavedatafromindia 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.

Ctstandsforcyclethresholds, 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.

Schoolsacrossindiahavebeen shutsincemarch21,theweekend before a national lockdown was announced by Prime Minister Narendra Modi on March 24, whichhaslimitedphysicalinteractionbetweenchildren,butwith some relaxation of movement restrictions,socialinteractionis set to increase.

Studies on Covid-19 prevalence in children have produced widely varying results. Large studiesfromiceland,thenetherlandsandspainanditalyshowed markedlylowersars-cov2prevalenceamongchildrenandyoung people,butstudiesfromsweden, theukandsomeareasinswitzerland 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 socialdistancingnormswithout supervision in crowded classrooms, canteens and playgrounds.thiscanledtoinfection clusters in schools, from where children can spread it to staff, families and communities or neighbours without developing severediseasethemselves,”said Drrajeshsagar,professorinthe department of psychiatry, All India Institute of Medical Sciences Delhi.