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countries are affected worldwide. · In the EU/EEA and the UK, 17 413 cases had been reported as of 11 March. Seven hundred and eleven cases reported by EU/EEA countries have died as of 11 March. Italy represents 58% of the cases (n=10 149) and 88% of the fatalities (n=631). · The 14-day cumulative notification rate of COVID-19, a measure of the prevalence of active cases in the population, is 3.28 per 100 000 population in the EU/EEA as of 11 March, ranging from low rates of 2 Disease background For information on COVID-19, please visit this page [15] on ECDC’s website. Novel coronavirus disease 2019 (COVID-19) In December 2019, a novel coronavirus (COVID-19) was detected in three patients with pneumonia connected to the cluster of acute respiratory illness cases from Wuhan, China. By the end of February 2020, several countries were experiencing sustained local transmission, including in Europe. Symptoms, incubation period, severity: The most commonly reported clinical symptom in laboratory-confirmed cases is fever (88%), followed by dry cough (68%), fatigue (38%), sputum production (33%), dyspnoea (19%), sore throat (14%), headache (14%) and myalgia or arthralgia (15%) [16]. Less common symptoms are diarrhoea (4%) and vomiting (5%). About 80% of reported cases in China had mild to moderate disease (including non-pneumonia and pneumonia cases), 13.8% had severe disease and 6.1% were critical (respiratory failure, septic shock, and/or multiple organ dysfunction/failure). Current estimates suggest a median incubation period from five to six days for COVID-19, with a range from one to up to 14 days. A recent modelling study confirmed that it remains prudent to consider the incubation period of at least 14 days [17,18]. Case fatality: Robust estimates for final case fatality risk for COVID-19 are still lacking and biased due to incomplete outcome data and the fact that initial detections were of mostly severe cases in most settings. Based on a large dataset from cases in China, the overall case fatality risk (CFR) among laboratory-confirmed cases was higher in the early stages of the outbreak (17.3% for cases with symptom onset from 1-10 January) and has reduced over time to 0.7% for patients with symptom onset after 1 February [16]. In data on diagnosed COVID-19 cases in China, Italy and South Korea, overall CFR was 2.3%, 2.8% and 0.5%, respectively, and increased with age in all settings, with the highest CRF among people over 80 years of age (14.8%, 8.2% and 3.7%, respectively) [19-21]. Viral shedding: Over the course of the infection, the virus has been identified in respiratory tract specimens 1-2 days before the onset of symptoms and it can persist for 7-12 days in moderate cases and up to 2 weeks in severe cases [22]. In faeces, viral RNA has been detected from day 5 after onset and up to 4 to 5 weeks in moderate cases. The virus has been detected also in whole blood [23], serum [24,25] saliva [26] and urine [27]. Prolonged viral RNA shedding has been reported from nasopharyngeal swabs, up to 37 days among adult patients [28] and in faeces, for more than one month after infection in paediatric patients [29]. It should be noted that viral RNA shedding does not directly equate with infectivity. Basic reproduction number (R0): The current estimates of the basic reproductive number R0 are between 2 and 3 in settings from China [17,30,31] and during the early stage of an outbreak on a cruise ship [32]. Infection in asymptomatic individuals: The virus has been detected in asymptomatic persons. On a rapidly evolving cruise ship outbreak, where most of the passengers and staff were tested irrespective of symptoms, 51% of the laboratory confirmed cases were asymptomatic at the time of confirmation [33]. In Italy, 44% of the laboratory-confirmed cases have been asymptomatic [34]. In Japan, 0.06% of reported cases have been asymptomatic [35]. These proportions based on nationally notified cases likely reflect laboratory testing algorithms rather than true estimates of asymptomatic infections. Based on Chinese data, the international WHO mission report indicates that up to 75% of initially asymptomatic cases will progress to clinical disease, making the true asymptomatic infection rather rare (estimated at 1-3%) [16]. Both viral RNA and infectious virus particles were detected in throat swabs from two German citizens evacuated from Hubei province on 1 February 2020, who remained well and afebrile seven days after admission to a hospital in Frankfurt [36]. Both a mother and a child in a family cluster remained asymptomatic (including normal chest CT images during the observation period) with qRT-PCR positive nasopharyngeal swab samples [37]. Similar viral load in asymptomatic versus symptomatic cases was reported in a study including 18 patients [38]. Persistent positivity of viral RNA in throat and anal swabs were reported in a asymptomatic female patient after 17 days of clinical observation and treatment [39]. Potential transmission from an asymptomatic person has been reported in a familial cluster of five COVID-19 patients hospitalised with fever and respiratory symptoms that had contact before their onset of symptoms with an asymptomatic family member, a young 20-year-old woman, upon her return from Wuhan [40]. She remained