Coronaviruses are a group of viruses that cause diseases in mammals and birds. In humans, viruses that cause respiratory infections - including the common cold - are usually mild. The rare form of novel coronavirus, such as SARS, MERS and new coronavirus, which broke out in Wuhan in 2019-20, may be fatal. In cattle and pigs, the coronavirus causes diarrhea. In chickens, they cause upper respiratory diseases. No vaccines or antiviral drugs have been approved for prevention or treatment.

Coronaviruses exist in the order of coronaviridae. They are envelope viruses with positive single stranded RNA genome and helically symmetric nucleocapsid. The genome size of coronavirus is about 26 to 32 thousand bases, which is the largest RNA virus.

The name "coronavirus" comes from the Latin word corona, which means corona or corona. It refers to the characteristic appearance of virus particles (virus bodies): their edges remind people of corona or corona.

The novel coronavirus, known as 2019-nCoV, was officially called the Wuhan coronavirus in 2019. It is an infectious virus that can cause 2019-nCoV acute respiratory disease (a respiratory tract infection). This is the cause of the continuous outbreak of Wuhan coronavirus in 2019-20 and has been designated as a global health emergency by the World Health Organization. Genome sequencing shows that it is a justice single stranded RNA coronavirus.

Many early cases are associated with large seafood and animal markets, and the virus is believed to be the origin of zoonoses. The genetic sequence of the virus was similar to that of SARS CoV (79.5%) and bat coronavirus (96%). Although intermediate hosts such as pangolins cannot be excluded, this makes it possible for bats to eventually originate.

The virus has spread from person to person. The coronavirus is mainly transmitted by close contact, especially by respiratory droplets caused by coughing and sneezing, and ranges from about 6 feet (1.8 m). Viral RNA was also found in fecal samples from infected patients. Even in the incubation period, the virus may be infectious, but this has not been confirmed, the World Health Organization (who) pointed out that "the transmission of asymptomatic cases may not be the main driving force at present".

During the continuous outbreak, the virus is commonly known as "coronavirus", "new coronavirus" and "Wuhan coronavirus", while the World Health Organization proposes to use the temporary name "2019 ncov". Concerned that the lack of an official name may lead to the use of biased informal names, the International Committee on Virology (ICTV) announced that it would introduce the appropriate official name for the virus in the second edition in February 2020, according to the WHO guidelines 2015.