Clinical characteristics of COVID-19
Page last reviewed: 7 September 2021
Detailed epidemiological information on laboratory-confirmed cases reported to The European Surveillance System (TESSy) are published in the ECDC weekly COVID-19 country report and the weekly COVID-19 surveillance report.
Symptoms and signs
An observational study of 1 420 patients with mild or moderate disease indicated that the most common symptoms were headache (70.3%), loss of smell (70.2%), nasal obstruction (67.8%), cough (63.2%), asthenia (63.3%), myalgia (62.5%), rhinorrhoea (60.1%), gustatory dysfunction (54.2%) and sore throat (52.9%) and fever (45.4%) . Olfactory and gustatory dysfunction have been identified as common symptoms with a 52.73% pooled prevalence across ten studies . Similarly, altered taste sensation was found among 49.8% of COVID-19 patients in a pooled analysis of five studies .
The latest International Severe Acute Respiratory and Emerging Infections Consortium (ISARIC) report on 60 109 hospitalised cases of COVID-19 across 43 countries found that the three most common symptoms at admission were history of fever (68.7% of patients), cough (68.5%), and/or shortness of breath (65.8%), and that 92% of those admitted experienced one or more of these. Additional COVID-19 symptoms at admission included fatigue (46.4%), confusion (27.3%), muscle pain (20.1%), diarrhoea (19.1%), nausea and vomiting (18.8%), headache (13.0%), sore throat (10.5%), loss or altered sense of taste (7.2%) or smell (6.2%) . Overall, the prevalence of symptoms was highest in people aged 30-60 years; the most common atypical presentation in older adults was confusion.
The most commonly reported symptoms in children are fever and cough [5-7]. Other symptoms include gastrointestinal symptoms, sore throat/pharyngitis, shortness of breath, myalgia, rhinorrhoea/nasal congestion and headache with varying prevalence among different studies [5-8].
Most cases of COVID-19 are mild or moderate and do not require hospitalisation or advanced medical care. Overall, 7.5% of COVID-19 cases diagnosed from August 2020 through May 2021 reported by EU/EEA countries to the European Surveillance System (TESSy) were hospitalised, although this varied by age, with hospitalisation rates of 1.3% in persons under 30 years, 3.9% in those 30-59 years, 12.8% in 60-69 years, 26.1% in 70-79 years and 34.9% in those 80 years and older. Overall, 0.9% of all COVID-19 cases reported, and 13.6% of hospitalised cases, were reported as severe, requiring ICU admission and/or oxygen supportive therapy. A strong age-gradient is also observed for severe hospitalisation, with higher rates in older age groups. Overall, the crude case-fatality rate among COVID-19 cases reported to TESSy since August 2020 is 1.9%, with rates well below 1% for cases under 60 years of age, 2% in those 60-69 years, 7.4% in those 70-79 years and 19% in those 80 years and older. Regularly updates on severity estimates by age group and sex are published as part of ECDC’s weekly surveillance report .
Patients with COVID-19 often report persisting symptoms or develop new symptoms after the acute infection is over . At least one symptom has been reported in up to 80% of individuals beyond two weeks after a confirmed COVID-19 diagnosis  and the UK Office of National Statistics estimates that 1 in 10 people testing positive for COVID-19 exhibit symptoms for a period of 12 weeks or longer after acute infection .
Persistence of symptoms beyond three weeks from the onset of symptoms is defined as ‘post-acute COVID-19’ and persistence of symptoms beyond 12 weeks is defined as ‘chronic COVID-19’ . The term ‘sub-acute or ongoing symptomatic COVID-19’ is proposed when symptoms persist for four to 12 weeks after acute COVID-19. However, other names have been used to describe conditions following acute COVID-19 (such as ‘post-COVID condition’ and ‘long COVID’) and there is not an internationally accepted definition yet. The spectrum of presentation, pathophysiology, clinical course, diagnosis, and management of these conditions is under investigation.
Prolonged symptoms may be due to delayed recovery from the acute infection, including post-ICU syndrome, ongoing infection, organ damage and sequelae due to complications (such as myocardial injury, pulmonary embolism, lung fibrosis, stroke etc), multisystem inflammatory syndrome (MIS), and post-viral fatigue syndrome [14,15], or a combination of the above.
Post-acute COVID-19 has manifestations from several organ systems. Symptoms from the respiratory tract include shortness of breath, cough, and sore throat. Decreased diffusing capacity and abnormalities in lung imaging are commonly observed. Cardiovascular presentations include chest pain and palpitations or tachycardia, as well as thromboembolic events. Neuropsychiatric conditions are common. Chronic fatigue, headaches and loss of smell are the most common symptoms of post-acute COVID-19, but cognitive symptoms, such as difficulty concentrating, sleep disturbances and depression are commonly reported . Manifestations from other organ systems, such as endocrine, gastrointestinal, renal, and skin, are reported less frequently. Increasing age, female sex and hospitalisation for acute COVID-19 are linked to a higher prevalence of prolonged symptoms . The prevalence of post-acute COVID-19 decreases over time since the acute presentation  but it is not possible to determine yet how long the symptoms may persist.
Prolonged symptoms are common in hospitalised patients with severe COVID-19 after discharge . Among patients discharged from hospital, decreased quality of life was observed in 44% of the patients and 10-30% required rehospitalisation over the months following discharge [18,19]. However, prolonged illness is also reported after mild COVID-19 , but the extent of the burden on the healthcare system of these cases is uncertain.
The burden of post-acute COVID-19 is expected to be high due to the high incidence of persisting symptoms and sequelae among the more than 30 million confirmed COVID-19 cases in the EU/EEA since the start of the pandemic and adding to the burden on the healthcare systems. Due to the multisystem nature of post-acute COVID-19, a need is foreseen in the coming years for multidisciplinary support for the diagnosis, treatment, rehabilitation, and support of people with post-acute COVID-19 . The burden of post-acute COVID-19 is expected to fluctuate depending on the incidence of acute COVID-19 during epidemic waves because the prevalence of post-acute COVID-19 decreases with time since the acute infection. Burden due to chronic sequelae is also expected in a sizeable minority of patients, especially those with severe COVID-19 who required hospitalisation or critical care and had complications such as stroke, myocardial infarction, or pulmonary fibrosis.