COVID-19 is a zoonotic illness caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus was previously known as 2019 novel coronavirus. The first cases were seen in the city of Wuhan, China in December 2019, and have been linked to the Huanan Seafood Wholesale Market 1,2,10. Person-to-person transmission occurs. The imaging findings are of pneumonia, often bilateral. No effective treatment or vaccine currently exists.
On 11 February 2020, the World Health Organization (WHO) officially renamed the clinical condition COVID-19 (a shortening of COronaVIrus Disease-19), which was announced in a tweet 15. Coincidentally, on the same day, the Coronavirus Study Group (CSG) of the International Committee on Taxonomy of Viruses renamed the virus "severe acute respiratory syndrome coronavirus 2" (SARS-CoV-2) 16,22.
The WHO has expressed reservations about the official virus name in view of its closeness to the name SARS. It has publicly stated it will not be using it, instead using "COVID-19 virus" or the "virus that causes COVID-19", however the scientific community is already using SARS-CoV-2 and it is likely that this will be gradually accepted by the wider world 22.
The WHO had originally called this emerging zoonotic infectious illness "novel coronavirus-infected pneumonia (NCIP)" and the virus itself had been named 2019 novel coronavirus (2019-nCoV) 1,2.
As of 23 February 2020, over 78,900 cases of COVID-19 have been confirmed worldwide, with the vast majority (~98%) in China, according to a Johns Hopkins online virus tracker 5.
The infection was declared a Public Health Emergency of International Concern (PHEIC) on 30 January 2020 by the WHO 7.
On 13 January 2020, the first confirmed case outside China was diagnosed, a Chinese tourist in Thailand 10. On 20 January, the first infected person in the United States was confirmed to be a man in the State of Washington who had recently returned from a visit to Wuhan 9. The disease has now been diagnosed in 30 territories, including Macau and Hong Kong, in five continents 5,13.
The mortality rate is about 2-3% 2,5 with currently 2467 confirmed deaths (23 February 2020) 5. There have now been 25 confirmed deaths outside mainland China, including eight in Iran, six in South Korea, three in Italy and one in France 5.
In the largest study to date, a paper published by the Chinese Center for Disease Control and Prevention (CCDC) analyzed all the cases diagnosed up to 11 February 2020, which came to 44,672 cases. Of these 1.2% were asymptomatic and 80.9% were classed as "mild". The overall mortality rate was found to be 2.3% 25.
In an article examining the first 425 infected cases in Wuhan, 56% of the infectees were male and the median age was 59 years 12. In this early cohort there were no children under 15 years old. Using this dataset, the group estimated that the R0 (basic reproduction number) of the novel coronavirus was 2.2, that is each infected individual - on average - causes 2.2 new cases of the disease. The incubation period in this group has been calculated to be 5.2 days on average 12.
NB: it is important to appreciate that the epidemiological parameters of the disease are likely to change as larger cohorts of infected people are studied.
Initial cases of COVID-19 presented as pneumonia, however it is now clear that some individuals, especially young children, remain asymptomatic, whilst others have mild upper respiratory tract symptoms only. Some also experience mild GI symptoms 18. However, its full spectrum of clinical effects remains to be determined 1,2,13. Symptoms and signs are non-specific:
The most common findings in a study of 138 hospitalized patients were 13:
In a study of 138 patients who had been hospitalized, 26% were admitted to the intensive care unit (ICU). The ICU patients tended to be older with more comorbidities 13.
SARS-CoV-2 was confirmed as the cause of COVID-19 on 9 January 2020 14. It is a member of the Betacoronavirus genus, one of the genera of the Coronaviridae family of viruses. Coronaviruses are enveloped single-stranded RNA viruses, that are found in humans, many other mammals and birds. These viruses are responsible for pulmonary, hepatic, CNS and intestinal disease.
The natural animal host of SARS-CoV-2 remains undetermined, and although the closest animal coronavirus by genetic sequence is a bat coronavirus, and this is the likely ultimate origin of the virus 11,19,26, the disease can also be transmitted by snakes 24.
Hitherto, six coronaviruses have been known to be responsible for human diseases, two are zoonoses, the severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), both of which may sometimes be fatal. The remaining four viruses are widespread in human society, causing the common cold.
COVID-19 is primarily transmitted in a similar way to the common cold, that is face to face, either from sneezing/coughing or close contact with infected individuals' bodily secretions 19.
A recent retrospective study of nine pregnant patients infected by SARS-CoV-2 did not show any evidence of intrauterine infection 21.
The primary findings on CT have been reported as 13,17:
- ground glass opacities (GGO) in all hospitalized patients
- crazy paving appearance (GGOs and inter-/intra-lobular septal thickening)
- air space consolidation
No mediastinal lymphadenopathy has been seen 17.
In one study, 18 of 21 patients (86%) with non-complicated COVID-19 pneumonia, in whom the temporal progression of the CT appearances in COVID-19 were studied, severity of lung abnormalities peaked at 10 days post symptom onset, with a gradual tail-off after this time 17. In another study of thirty six patients, HRCT showed rapid changes over time with fibrous stripes appearing upon improvement in the disease course 24.
Treatment and prognosis
No specific treatment or vaccine exists for COVID-19 (as of February 2020). Therefore in the meantime, resources have been concentrated on public health measures, to prevent further interhuman transmission of the virus. This has required a multipronged approach and for individuals includes meticulous personal hygiene, fitted masks, and the avoidance of large crowds/crowded environments 11.
In healthcare facilities, concerted efforts are required to effect rapid diagnosis, quarantine infected cases and provide effective supportive therapies. This will encompass empirical treatments with antibiotics, antivirals, steroids and supportive measures. Mechanical ventilation and extracorporeal membrane oxygenation (ECMO) have also been used where clinically necessary.
Whilst specific antiviral therapies for SARS-2-CoV do not currently exist, the combination of the protease inhibitors, ritonavir and lopinavir, or a triple combination of these antiviral agents with the addition of ribavirin, showed some success in the treatment of SARS 20, and early reports suggest similar efficacy in the treatment of COVID-19 23.
Vaccines for the coronaviruses have been under development since the SARS outbreak, but none are yet available for human patients 11,26. A phase I trial in humans of a potential vaccine against MERS-CoV has already been performed in the UK 26.
In the earliest studies, mortality rate was estimated as 3%, although later data, suggests it as being slightly closer to 2% 2,5. In a study of the first 44,672 diagnosed cases in mainland China, the fatality rate was found to be 2.3% 25.
In a Chinese study looking at 138 hospitalized patients only, in-hospital mortality was higher at 4.3% 13.
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