2. The Epidemiology of COVID-19
On 31 December 2019, Wuhan Municipal Health Commission reported a number of unknown pneumonia cases related to Huanan Seafood Wholesale Market, 27 cases were hospitalized, seven of which were in serious condition [1]. On 5 February 2020, Wuhan Municipal Health Committee reported that 59 cases of viral pneumonia with unknown etiology were detected in Wuhan, including seven severe cases, but no clear evidence was found for “human-to-human” transmission [8]. On Jan 11, Wuhan Municipal Health Committee issued a new report confirming that the pathogen of the viral pneumonia of unknown cause was initially determined as a new coronavirus [9]. On 20 February 2020, it was officially confirmed that “human-to-human” transmission and nosocomial infection had occurred [2,3].
Since 16 February 2020, the cumulative COVID-19 case number increased quickly; meanwhile, the daily emerging case number increased steadily to 3886 on 4 February 2020, and then fluctuated to 2015 on 11 February 2020. The fatality cases number increased steadily to 2004 cases on 18 February 2020. The cumulative and daily emerged cases number jumped to 59,804 and 15,152, respectively, on 12 February 2020 (Figure 1). This fierce growth of cumulative and daily emerged cases number in one day is due to the improvement of diagnosis standard for confirmed cases in Hubei province, in which the suspected cases with pneumonia imaging characteristics are categorized as clinical diagnosis cases. As a result, the patients can receive standard treatment as soon as possible. All data are from the National Health Commission of the People’s Republic of China [10].
The COVID-19 resulted in much lower mortality (about 2.67% up-to-date) among the confirmed cases, compared with Severe Acute Respiratory Syndrome (SARS) at 9.60% (November 2002–July 2003) and Middle East Respiratory Syndrome (MERS) at 34.4% (April 2012–November 2019) (Table 1). The median ages for the patients of COVID-19, SARS, and MERS are 55.5, 41.3, and 52.8 years old, respectively. COVID-19 and MERS patients share similargender composition of females (32%) and males (67%), but SARS patients show almost the same proportion of males (46.9%) and females (53.1%).
According to the “Diagnosis &Treatment Scheme for Novel Corona Virus Pneumonia (Trial) 6th Edition”, the source of infection is majorly the COVID-19 patients, even the asymptomatic patients can also be the source of infection. The transmission way is majorly through respiratory droplets and contacting. People are generally susceptible to this virus.