COVID-19 (coronavirus disease-19) is a zoonotic illness caused by a novel coronavirus, which is called severe acute respiratory syndrome coronavirus 2 or SARS-CoV-2. 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 can occur. The imaging findings are of pneumonia, often bilateral. No effective treatment or vaccine currently exists.
On February 11th 2020, the World Health Organization (WHO) officially named the condition COVID-19 or coronavirus disease-19, which was announced in a tweet 15. On the same day the International Committee on Taxonomy of Viruses renamed the virus "severe acute respiratory syndrome coronavirus 2" or SARS-CoV-2 16.
The WHO had originally called this emerging zoonotic infectious illness "novel coronavirus-infected pneumonia (NCIP)" and the virus had been named 2019 novel coronavirus or 2019-nCoV 1,2.
As of February 10 2020, over 43,000 cases of COVID-19 have been identified worldwide, with the vast majority (~99%) in China, according to a Johns Hopkins online virus tracker 5.
The infection was declared a Public Health Emergency of International Concern (PHEIC) on January 30th 2020 by the WHO 7.
On January 13 2020, the first confirmed case outside China was diagnosed, a Chinese tourist in Thailand 10. On January 20, 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 28 territories, including Macau and Hong Kong, in five continents 5,13.
The mortality rate is about 2-3% 2,5 with currently 1018 confirmed deaths (February 11, 2020) 5. Only two confirmed deaths have been outside mainland China, one in Hong Kong, and a second one in the Philippines 5.
A recent modelling study suggested that the true number of cases of infection is much higher than published official figures, being greater than 75,000 infected persons in Wuhan 8.
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.
COVID-19 primarily presents as pneumonia, however, its full spectrum of clinical effects remains to be determined 1,2,13. Symptoms 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.
The recently identified 2019-nCoV was confirmed as the cause of novel coronavirus-infected pneumonia on January 9 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 2019-nCoV remains undetermined 11.
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.
The primary findings on chest radiograph and CT are those of pneumonia 3. 75% of cases have presented with bilateral pneumonia 6.
Treatment and prognosis
No specific treatment or vaccine exists for this emerging illness (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.
Vaccines for the coronaviruses have been under development since the SARS outbreak, but none are yet available for human patients 11.
In the earliest studies, mortality rate was estimated as 3%, although later data, suggests it as being slightly lower at 2%. In a Chinese study looking at 138 hospitalized patients only, mortality was 4.3% 2,5,13.