Covid-19 researchers warn children may be as infectious as adults

AS WA prepares to review its Covid-19 schools policy and role out a study on transmission of the disease in schools an overseas study warns children may be as infectious as adults.

One of the authors of the overseas study An analysis of SARS-CoV-2 viral load by patient age is virologist Christian Drosten who advises German Chancellor Angela Merkel and Germany’s Health Minister Jens Spahn on the country’s response to the virus.

The study by Professor Drosten, who was among those who identified the Sars virus in 2003, and the other authors examines the relationship between patient age and SARS-CoV-2 viral load.

They concluded viral loads in the very young did not differ significantly from those of adults.

“Based on these results, we have to caution against an unlimited re-opening of schools and kindergartens in the present situation (as) children may be as infectious as adults,’’ the study said.

The authors said there were reasons to argue against the notion of adult-like infectivity in children, such as the fact that asymptomatic children do not spread the virus by coughing and have smaller exhaled air volume than adults.

“But there are other arguments that speak in favour of transmission, such as the greater physical activity and closer social engagement of children.’’

Their study examined data from 3712 (6.2 per cent) patients with a positive real-time RT-PCR (1) result who were among 59,831 patients tested for Covid-19 infection between January to April 26 from virology laboratories at Charité and Labor Berlin.

They also recommended the collecting and evaluating of more viral load data from testing laboratories to achieve more robust statistical assessments and independent confirmation of the present results.

Their conclusion is in contrast to COVID-19 in schools – the experience in NSW the study the chief medical officer Brendan Murphy relied on to say there was no evidence of significant infection in children and no evidence of significant transmission among children in schools when the Prime Minister Scott Morrison started calling for parents to send their children back to school.

The study by the National Centre for Immunisation Research and Surveillance (NCIRS) with support from NSW Ministry of Health and NSW Department of Education said the investigation involved 15 schools (10 high school and five primary schools) where a total of 18 Covid-19 cases (nine students and nine staff) were identified between March 5 and April 3.

The study said its findings were preliminary but suggested the spread of Covid-19 within NSW schools had been very limited and that SARS-CoV-2 transmission in children in schools appeared considerably less than seen for other respiratory viruses, such as influenza.

The public health staff identified 863 close contacts in the 15 schools.

“Of the 863 close contacts, only two students have been identified as secondary cases.

“One of these was diagnosed by nose/throat swab testing and one had a positive antibody test four weeks after their exposure,’’ the NSW study said.

“A review showed that it was most likely, but not certain, that these two children were infected by transmission in the school environment.

“Overall only one of 695 individuals was identified to have been infected following close contact with a school case in these 10 high schools.

“Overall only one of 168 individuals was identified to have been infected following close contact with a school case in these five primary schools.’’

The study by the team including Professor Drosten said measures to curb the spread of SARS-CoV-2 by non-pharmaceutical interventions were beginning to show results in many countries.

But now along with the relaxing of physical distancing there was increasing discussion about the contribution of school and kindergarten closures to the reduction of transmission rate and to the expected rebound when they reopened.

“Early transmission clusters were started by travellers of adult age, making children less likely to be index cases in households, ‘’ the study said.

“Another circumstance making children less likely to carry the virus into households is that kindergartens and schools were closed early in the outbreak in Germany.

“These combined effects will cause children to be more likely to receive rather than spread infections in households for purely circumstantial reasons.

“This observation may be misunderstood as an indication of children being less infectious.’’

The NSW school study said it was notable that on March 23 the NSW Premier Gladys Berejiklian advised that although schools remained open, parents were encouraged to keep their children at home for online learning.

“After this date face-to-face attendance in schools decreased significantly and this may have impacted the results of this investigation,’’ the NSW study said.

“Furthermore, school holidays commenced in NSW on Friday, April 10 for two weeks.

“Analysis of data collected here is ongoing and a full peer reviewed report is being prepared for publication.

“As a phased re-introduction of face-to-face learning in schools is planned for early Term 2 from May 11, it will be important to continue these detailed investigations to monitor the transmission of Covid-19 in schools.’’

Head of the Kirby Institute’s Biosecurity Program Professor Raina MacIntyre, whose research includes epidemic response and emerging infectious diseases, said she believed silent transmission played a role in the spread of Covid-19.

On April 21 Professor MacIntyre in an online presentation The Covid-19 pandemic update: transmission, herd immunity and is an exit strategy possible? said the reason why there was silent transmission was 80 per cent of people had mild infection.

“So you can have a few chains of transmission happening where most of the people are getting mild infections and statistically you won’t start seeing those 20 per cent of severe infections until the epidemic has got big enough and grown enough for it to start impacting your health system to start getting noticed.’’

On April 1 when announcing a new study to test for Covid-19 in schools WA  Health Minister Roger Cook said all available evidence indicated schools were safe but the McGowan Government’s commitment to the study should provide the community with further reassurance that it was taking reasonable steps to detect any undiagnosed Covid-19 in WA and better understand how schools were affected by the virus.

The WA study called Detect is a partnership between the departments of Health and Education with the Telethon Kids Institute and swabbing of the teachers and students taking part is expected to start in coming weeks.

Education and Training Minister Sue Ellery said to date WA had had no student-to-student or student-to-teacher transmission of Covid-19 and the government wanted that to continue.

“But this study will play an important role in establishing whether asymptomatic transmission may occur and which groups may be at greater risk,’’ she said.

The WA government is expected to give an update on its Covid-19 schools policy next week.

• (1) According to the International Atomic Energy Agency real time RT-PCR is a nuclear-derived method for detecting the presence of specific genetic material from any pathogen, including a virus.

Originally, the method used radioactive isotope markers to detect targeted genetic materials, but subsequent refining has led to the replacement of the isotopic labelling with special markers, most frequently fluorescent dyes.

With this technique, scientists can see the results almost immediately while the process is still ongoing; conventional RT-PCR only provides results at the end.