Table 1

Diagnostic criteria used in a large paediatric series of 2143 childhood COVID-19 cases in China6

Severity of illness	Description of illness
1. Asymptomatic	Positive nose/throat PCR for SARS-CoV-2 in a child with no clinical symptoms or signs and with normal chest imaging if performed.
2. Mild	Symptoms of acute upper respiratory tract infection, including fever, fatigue, myalgia, cough, sore throat, runny nose and sneezing. Physical examination shows congestion of the pharynx and but no auscultory abnormalities. Some cases may present with no fever or have only gastrointestinal symptoms such as nausea, vomiting, abdominal pain and diarrhoea.
3. Moderate	Presentation with pneumonia, fever and cough (initially dry then productive), some may have wheezing or transmitted respiratory noises, but no obvious hypoxaemia such as shortness of breath. Some cases may have no clinical symptoms or signs, but chest CT shows lung lesions, which are subclinical.
4. Severe	Early respiratory symptoms such as fever and cough may be accompanied by gastrointestinal symptoms such as diarrhoea. Disease usually progresses around 1 week, and dyspnoea occurs, with central cyanosis. Oxygen saturations are less than 92% in air, with other hypoxia manifestations.
5. Critical	Rapid progression to acute respiratory distress syndrome or respiratory failure, with or without shock, encephalopathy, myocardial injury or heart failure, coagulation dysfunction and acute kidney injury. Organ dysfunction may be life threatening.