COVID-19 patients are the main source of infection, and severe patients are considered to be more contagious than mild ones
Asymptomatically infected persons proven to shed infectious virus, may also be potential sources of infection
Spectrum of infection
COVID-19 has been considered as a type of self-limiting infectious disease, and most cases with mild symptoms can recover in 1–2 weeks
It can cause five different outcomes: asymptomatically infected persons (1.2%); mild to medium cases (80.9%); severe cases (13.8%); critical case (4.7%); and death (2.3% in all reported cases)
Clinical features
Analysis of 1324 laboratory confirmed cases showed that fever (87.9%) and cough (67.7%) were the most common symptoms followed by dyspnea, fatigue, sputum production, headache, hemoptysis and diarrhea
Epidemiological characteristics in China
The initial outbreak (8 December 2020) only occurred in Wuhan and its surroundings in Hubei Province
As of January 30 COVID-19 had spread to all 31 provinces in mainland China
The number of reported cases rose rapidly after 10 January 2020, and reached a peak on 12 February 2020
Tibet and Qinghai Provinces have had no confirmed cases since 21 February 2020 and 24 February 2020, respectively
On 18 March 2020, “0” new confirmed cases was first reported in Hubei Province, and a total of 24 provinces in mainland China had consecutively reported “0” new confirmed cases
Until 23 March the number of new confirmed cases have mainly come from abroad and eight provinces have had no confirmed cases
China CDC data showed that patients were mainly concentrated at the age of 30–79, accounting for 89.8%, 88.6%, and 86.6% of confirmed cases in Wuhan, Hubei, and mainland China, respectively
The proportion of infected healthcare workers and farmers was 2.09% and 22%, respectively
The total case-fatality rate was 2.3% of 44,672 confirmed cases, while the total case-fatality rate in Hubei and its surroundings was 2.9% and 0.4%
In contrast, the total case-fatality rate of SARS and MERS was 9.6% and 34%
In all COVID-19 patients over 80-years old, the case-fatality rate was as high as 14.8%
The case-fatality rate of males and females was 2.8% and 1.7%
The case-fatality rate of cases with cardiovascular disease, diabetes, chronic respiratory disease, hypertension, and cancer was 10.5%, 7.3%, 6.3%, 6.0%, and 5.6%, respectively
For healthcare workers, the case-fatality rate was approximately 0.17% of 3019 cases
Other regions
The total case-fatality rate of global cases outside China is 4.5%
Higher case-fatality rates were found in Italy (9.3%), Iran (7.8%), and Spain (6.0%)
Routes of transmission
Respiratory droplets and contact transmission are considered to be the main transmission routes
SARS-CoV-2 can be detected in the urine and stool of laboratory confirmed patients, implying a risk of fecal–oral transmission
There is still no evidence that SARS-CoV-2 can be transmitted from mother to baby during pregnancy or childbirth
Herd susceptibility
In mainland China, 30~65-year-old persons account for 71.45% and children under 10-years-old account for 0.35%
Asthma, diabetes, cardiovascular diseases, cancer, smoking and obesity are other risk factors
High risk population
Healthcare workers and the family members of patients are considered at high risk
