Globally our understanding of how children are affected by COVID-19 has evolved. Once thought of as peculiarly resistant to the disease, there is now an emerging view that they are not. Children appear to be infected at comparable rates to adults, and as they are more likely to be asymptomatic, or have mild symptoms, their potential as stealthy sources of community transmission has experts increasingly concerned.

Back in Australia, however, pet theories that children are not infectious are perpetuated by senior health authorities and media voices. These theories, used as the basis for political and economic arguments to prematurely re-open schools, dominate the national discourse in defiant ignorance of the global experience.

Maybe it's time to ask why.

In the early phase of the pandemic it was noted that children were significantly under-represented in cases presenting to hospital, and those cases tended to be mild. This led to speculation that children may not be a factor in community transmission of the coronavirus.

However recent data and reporting is quashing that early speculation and leading to a less surprising conclusion: children are susceptible to COVID-19, also at risk of serious health issues, and can themselves be infectious.

On March 17th the New York Times reported on a study of more than 2,000 children infected by coronavirus in China. In addition to finding that a third of the children fell moderately sick (with pneumonia and lung problems revealed by CT scan), it also found 6% developed serious illness, including one 14-year-old boy who died.

A paediatrician who was asked to comment on the report stated:

“The main conclusion is that children are infected at rates that may be comparable to adults, with severity that’s much less, but that even within the kids, there’s a spectrum of illness and there’s a handful that require more aggressive therapy.”

Another point of note is that 60 percent of the 125 children who became very ill were 5 years or younger, and more than half of those were infants under 12 months.

Stories have also emerged of infants with very mild symptoms and high viral loads, such as a 6-month old in Singapore as reported by the Los Angeles Times.

A baby with coronavirus was treated at the Wuhan Children’s Hospital in China earlier this month.Credit...China Daily/Reuters

More recently, on April 1st, the BBC ran an in-depth feature: "Why children are not immune to Covid-19". In it Andrew Pollard, professor of paediatric infection and immunity at the University of Oxford, was asked whether children can be infected with the coronavirus:

At the beginning of the pandemic, it was thought that children are not getting infected with the coronavirus, but now it is clear that the amount of infection in children is the same as in adults. It’s just that when they do get the infection they get much milder symptoms.

Another expert quoted in the piece, Graham Roberts, an honorary consultant paediatrician at the University of Southampton, was asked whether children with mild or no illness can transmit the coronavirus to others:

Many think that children are at low risk and we don’t need to worry about them, and yes, that is true for children who don’t have chronic medical conditions like immunodeficiencies. What people are forgetting is that children are probably one of the main routes by which this infection is going to spread throughout the community.
Children with very mild disease are probably going to be one of the major contributors to spreading the virus across the population. This is why schools closing are crucial to reducing the rate at which the pandemic spreads across the UK.

This is borne out by a recent CDC report on US paediatric Covid-19 cases from April 10th: "Coronavirus Disease 2019 in Children — United States, February 12–April 2, 2020" which states that "children are at similar risk of infection as the general population" and concludes in its summary that "patients with less serious illness and those without symptoms likely play an important role in disease transmission".

On the same day reporting from Israel reflected the CDC's conclusions, in 'Silent spreaders': Almost a third of infected kids under 9 are asymptomatic.

Is it surprising that we are seeing data, opinions and analysis converge on the idea that children are susceptible and infectious after all? Jonathan Ball, a professor of molecular virology, wrote in "What scientists know so far about the effects of coronavirus on children" that:

Like many of my colleagues, I could see no obvious reason why children weren’t being infected: this was a virus spread by the respiratory route, not through a process unique to adults. If significant numbers of children were infected and suffered very minor cold-like symptoms, then their potential to spread the virus was immense.
Photo credit: Kelly Sikkema @kellysikkema via unsplash.com

In a global pandemic defined by a highly infectious disease with asymptomatic characteristics, the reasonable and intuitive default is to assume children are vulnerable and have the potential to be infectious.

This leads us to the shaky foundation of Dr Brendan Murphy's medical advice on schools remaining open in Australia: that it is safe to do so as there is 'no good evidence' of child infectiousness and school transmission. His advice relies on an argument from ignorance, which in one form simply tries to convince you a proposition is true because it has not yet been proven false.

In this instance Murphy, Morrison and the AHPPC want us to assume children are not infectious because hard evidence is yet to materialise in Australia that they are (even though it is plausible and highly likely - something Murphy himself stated in a recent interview on ABC's Insiders).

While hard evidence for any assumption about Covid-19 is difficult to come by at such an early phase of a pandemic, from a public health policy perspective the burden of proof should be on Murphy and the AHPPC to demonstrate that children are not infectious.

All of this begs the question, why do Murphy and Morrison want us to accept a risky reversal of common sense and the shifting of burden of proof? The motivations appear firmly political, risking far greater long term economic damage along with unacceptable health risks for short term economic gain, by urging the premature full re-opening of schools.