The photograph posted by 15-year-old Hannah Watters caused a furoreAn excited or angry reaction. It was originally an Italian word meaning "rage" or "madness".. It showed a corridor at North Paulding High School in Georgia, with scores of students crowding together as they walked along.

Hardly any of them were wearing masks; social distancing was non-existent. The school authorities were so angry and mortifiedExtremely embarrassed. The phrase "mortify the flesh" is used of people who deprive themselves of physical comforts - or inflict pain on themselves - to focus on spiritual matters. that they suspended Hannah - though they later reinstated her.

In the wake of the photograph came the news that at least 97,000 children in the US had tested positive for Covid-19 in the last two weeks of July alone. In total, 338,000 have been found to be infected since the pandemic began.

What experts and politicians disagree on is how dangerous infections in children are for the population as a whole.

Britain's education secretary, Gavin Williamson, has declared that there is "little evidence that the virus is transmitted at school". Consequently, the UK government has ruled that schools should reopen next month. One of its advisers, Professor Russell Viner, says that this is "one of the least risky things we can do" in easing the lockdown.

There is no doubt that far fewer children become severely ill with the disease than adults. Less than 2% of confirmed cases of Covid-19 in the US, China, and Italy have been under-18s. The largest study done so far, which looked at 55,000 people hospitalised with the disease, found that a mere 0.8% were under the age of 19.

A harder question is how likely they are to pass it on to others.

A Chinese study at the start of the year suggested children under-10 were just as likely to catch the virus as adults; a German study concluded that they could be equally infectious. The worry was that they might be transmitting it without anyone realising because they did not show any symptoms.

Other studies, however, have been more optimistic. Another Chinese report, which focused on infected families, concluded that probably none of them had been given the disease by children.

Similarly, a report on an outbreak in the French AlpsThe Alps are Europe's biggest mountain range, stretching for 750 miles across eight countries: France, Switzerland, Italy, Monaco, Lichtenstein, Austria, Germany, and Slovenia. found that a child with the virus had had contact with more than 100 people without passing it on to any of them. "It would be almost unheard of for an adult to be exposed to that many people and not infect anyone else," says Alasdair Munro, a researcher at University Hospital Southampton.

Australian scientists who looked specifically at cases spreading from schools to the wider community found nine students and nine teachers with the virus. Of the 850 people they had been in contact with, only two had contracted it.

A worldwide team of scientists concluded after reviewing all the available research: "The role of children in transmission is unclear, but consistent evidence is demonstrating a lower likelihood of acquiring infection, and lower rates of children bringing infections into households."

No. Children are at a lower risk of catching and spreading Covid-19 than other diseases. A Queensland University
virologistSomeone who studies viruses. In Latin, "virus" means a poison or slimy liquid., who collated studies from several different countries, concluded that a child was the first person to fall sick in only 8% of infected households - compared to 50% in outbreaks of H5N1 bird flu.

Yes. Children just get tested less because they have fewer symptoms. They have a lower rate of infection at present precisely because schools have been closed. On top of this, schools are important meeting places for adults such as teachers and parents. The risk to them and their families will increase significantly.

Furore - An excited or angry reaction. It was originally an Italian word meaning "rage" or "madness".

Mortified - Extremely embarrassed. The phrase "mortify the flesh" is used of people who deprive themselves of physical comforts - or inflict pain on themselves - to focus on spiritual matters.

French Alps - The Alps are Europe's biggest mountain range, stretching for 750 miles across eight countries: France, Switzerland, Italy, Monaco, Lichtenstein, Austria, Germany, and Slovenia.

Virologist - Someone who studies viruses. In Latin, "virus" means a poison or slimy liquid.