SARS-CoV-2 belongs to a family of single-stranded RNA viruses known as coronaviridae, a common type of virus which affects mammals, birds and reptiles.
In humans, it commonly causes mild infections, similar to the common cold, and accounts for 10–30% of upper respiratory tract infections in adults[4]. More serious infections are rare, although coronaviruses can cause enteric and neurological disease[5]. The incubation period of a coronavirus varies but is generally up to two weeks[6].
Previous coronavirus outbreaks include Middle East respiratory syndrome (MERS), first reported in Saudi Arabia in September 2012, and severe acute respiratory syndrome (SARS), identified in southern China in 2003[7],[8]. MERS infected around 2,500 people and led to more than 850 deaths while SARS infected more than 8,000 people and resulted in nearly 800 deaths[9],[10]. The case fatality rates for these conditions were 35% and 10%, respectively.
SARS-CoV-2 is a new strain of coronavirus that has not been previously identified in humans. Although the incubation period of this strain is currently unknown, the United States Centers for Disease Control and Prevention indicate that symptoms may appear in as few as 2 days or as long as 14 days after exposure[6]. Chinese researchers have indicated that SARS-CoV-2 may be infectious during its incubation period[11].
