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1. Epidemiology

On 31 December 2019, the World Health Organization (WHO) was informed of a cluster of cases of pneumonia of unknown cause detected in Wuhan City, Hubei Province, China.

On 12 January 2020 it was announced that a novel coronavirus had been identified in samples obtained from cases and that initial analysis of virus genetic sequences suggested that this was the cause of the outbreak. This virus is referred to as SARS-CoV-2, and the associated disease as COVID-19.

As of 16 March 2020 (9:00am), over 165,000 cases have been diagnosed in 156 countries and areas (including mainland China), with a total of over 6,400 fatalities. Of these totals, over 84,500 cases and more than 3,000 deaths have been reported from countries outside mainland China. Within China, 84% of cases reported to date are in Hubei Province.

See the WHO Coronavirus dashboard for country by country information. WHO also publishes a daily international situation report.

The total number of confirmed cases in the UK is published by the Department of Health and Social Care.

2. Virology

Coronaviruses are a large family of viruses with some causing less-severe disease, such as the common cold, and others causing more severe disease such as Middle East respiratory syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS) coronaviruses.

2.1 Nomenclature and characterisation

On 11 February, WHO named the syndrome caused by this novel coronavirus COVID-19 (Coronavirus Disease 2019) using its best practice guidance.

The Coronavirus Study Group (CSG) of the International Committee on Taxonomy of Viruses has designated the aetiological agent ‘severe acute respiratory syndrome coronavirus 2’ (SARS-CoV-2). Characterisation of SARS-CoV-2 is ongoing. Initial information shared by China and WHO indicates that SARS-CoV-2 is a beta-coronavirus that is genetically similar to SARS-like coronaviruses obtained from bats in Asia.

3. Transmission

The source of the outbreak has yet to be determined. Preliminary investigations identified environmental samples positive for SARS-CoV-2 in Huanan Seafood Wholesale Market in Wuhan City, however some laboratory-confirmed patients did not report visiting this market. A zoonotic source to the outbreak has not been identified yet, but investigations are ongoing.

Although evidence is still emerging, information to date indicates human-to-human transmission is occurring. Hence, precautions to prevent human-to-human transmission are appropriate for both suspected and confirmed cases (see infection prevention and control guidance).

We do not know the routes of transmission of COVID-19; however, other coronaviruses are mainly transmitted by large respiratory droplets and direct or indirect contact with infected secretions. In addition to respiratory secretions, other coronaviruses have been detected in blood, faeces and urine.

Under certain circumstances, airborne transmission of other coronaviruses is thought to have occurred via unprotected exposure to aerosols of respiratory secretions and sometimes faecal material.

4. Clinical features

Initial clinical findings from patients to date have been shared by China and WHO. Fever, cough or chest tightness, and dyspnoea are the main symptoms reported. While most patients have a mild illness, severe cases are also being reported, some of whom require intensive care.

A variety of abnormalities may be expected on chest radiographs, but bilateral lung infiltrates appear to be common (similar to what is seen with other types of viral pneumonia).


Adapted from Public Health England

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