Table 1.

Characteristics of coronaviruses that infect humans

Coronavirus	Date discovered	Dated diverged from common ancestor	Class/ genera	Symptoms	Transmission	Incubation period (days)	Risk Factors
HCoV-229E	1966, Chicago	1800s [6]	Alpha	Common cold symptoms: rhinorrhoea, nasal congestion, sore throat, headache and chills [7]. Occurrences of lower respiratory tract infection (LRTI) mainly in children [8]	Respiratory	2-4 [7]	Immunocompromised, children, elderly.
HCoV-OC43	1967	1850-1900 [9]	Beta	Common cold symptoms. Higher rates of LRTI in adults than HCoV-229E [10]	Respiratory	2-4 [7]	Immunocompromised, children, elderly.
SARS-CoV	2002, Guangdong	1985-1998 [9]	Beta	Fever, dry cough, headache, dizziness, rhinorrhoea, myalgia, chills, rigors, diarrhoea, vomiting. LRTI, acute respiratory distress syndrome (ARDS), shock, multi-organ failure [11]	Mainly Respiratory. Faeces-oral, to a lesser extent [12]	2-7 [13]	Advanced age, male sex [14]. No recorded deaths in children and teenagers [11].
HCoV-NL63	2004, Netherlands	1200s [9]	Alpha	Common cold symptoms [7], LRTI [15]	Respiratory	2-4 [7]	Immunocompromised, children, elderly.
HCoV-HKU1	2005, Hong Kong	1950s [9]	Beta	Common cold symptoms [7], diarrhoea, vomiting [16], childhood febrile seizures [17]	Respiratory	2-4 [7]	Immunocompromised, children, elderly, smoking, inhaled corticosteroids [16].
MERS-CoV	2012, Saudi Arabia	2006 [9]	Beta	Fever, chills, cough, myalgia and gastrointestinal symptoms LRTI, ARDS, multi-organ failure, renal failure [18]	Respiratory. Requires close and prolonged contact [19]	2-14 [20]	Advanced age, male sex, chronic conditions (present in 75% of patients) such as diabetes, obesity, hypertension, lung conditions, cardiac conditions [18,21].
SARS-CoV-2	2019	Not known	Beta	Fever, dry cough, dyspnoea, myalgia and fatigue [22]. Less gastrointestinal involvement than SARS and MERS [23]	Primarily respiratory droplets. To a lesser extent: faecal-ran and through eyes [24]. Airborne transmission during aerosol generating procedures. Airborne transmission in indoor settings with poor ventilation under investigation [25]	5-6 d on average. Up to 14 d [25]	Advanced age, male sex. Co-morbidities (present in 20%-51% of patients): hypertension, diabetes, cardiovascular disease, pulmonary disease and malignancy [26].