Primary school-aged children infected with the coronavirus have much smaller viral loads than adults with Covid-19, a study has found.
Viral load — the amount of virus a person harbours in their nose and throat — is believed by some scientists to be linked to transmissibility, although there is debate over these claims.
Data from public health officials in the Netherlands reveals over-80s have a viral load 16 times bigger than than children under the age of 12.
Rapid antigen tests, like ones suggested for use in schools and airports, are also likely to be less accurate for children than adults, due to this smaller load, the researchers say.
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More than a quarter of a million people in northern Holland were tested between January 1, 2020 and December 1, 2020.
Of these tests, 211,933 were carried out by qualified healthcare professionals, with viral load data available for 18,290.
All of these swabs were processed by the same regional laboratory in the Netherlands to ensure the tests were analysed in the same way.
‘To our knowledge this is the first study to evaluate SARS-CoV-2 viral load distributions in a large number of patients from different patient categories,’ the researchers write in their study, which has not yet been peer-reviewed and is published online as a pre-print.
‘Our data present a clear relation between age and SARS-CoV-2 viral load, with children (less than 12 years) showing lower viral loads independent of sex and symptom duration.’
More than 2,500 of the people tested were younger than 20 and 238 of these were younger than 12, equivalent to primary school age.
One metric used to quantify viral load is Cp, which indicates how many cycles of PCR — which replicates and amplifies genetic material — is needed before the virus could be detected.
The higher the figure, the lower the viral load, as it indicates how many cycles of amplification were required.
In the study, the researchers note the difference between the average Cp figure for over-80s and under-12s is more than four cycles, equivalent to a 16-fold increase.
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