Table 1.

Case definition in the SARS-CoV-2 delta variant outbreak in Jingmen City, Hubei Province, China in August 2021.

Terms	Definition
Confirmed case	An individual who had positive PCR result of SARS-CoV-2 and COVID-19 related clinical symptoms (National Health Commission of the People's Republic of China, 2021a).
Asymptomatic infection	An individual who had positive PCR result of SARS-CoV-2 without clinical symptom (National Health Commission of the People's Republic of China, 2021a).
Close contact	An individual who was in contact without effective protection with someone with COVID-19 starting 4 days before the infected person developed symptoms or the sampling date if they did not have symptoms such as living, eating, working, traveling, and attending social activities (National Health Commission of the People's Republic of China, 2021a).
Mild COVID-19 case	A confirmed case with mild clinical symptoms, but without signs of pneumonia on chest imaging (National Health Commission of the People's Republic of China, 2021b).
Moderate COVID-19 case	A confirmed case with fever or respiratory symptoms, and imaging manifestations of pneumonia (National Health Commission of the People's Republic of China, 2021b).
Severe COVID-19 adult case	A confirmed case who met at least one of the following criteria: respiratory rate ≥30 times/min; oxygenation index ≤300 mmHg; resting oxygen saturation ≤93%; clinical symptoms were progressively aggravated and the lesion on lung had significantly progressed over 50% on chest imaging within 24–48 h (National Health Commission of the People's Republic of China, 2021b).
Severe COVID-19 child case	A confirmed case who met at least one of the following criteria: persistent high fever for more than 3 days; shortness of breath excluded the effects of fever and crying (respiratory rate in different ages: <2 months: ≥60 times/min; 2–12 months: ≥50 times/min; 1–5 years: ≥40 times /min;>5 years: ≥30 times/min); resting oxygen saturation ≤93%; assisted breathing; lethargy and convulsions; refusing food or feeding difficulties and dehydration (National Health Commission of the People's Republic of China, 2021b).