Coronaviruses are a family of viruses known for containing strains that cause potentially deadly diseases in mammals and birds.

In humans they're typically spread via airborne droplets of fluid produced by infected individuals.

Of the seven coronaviruses kown to infect humans, four spread with seasonal regularity, causing anything from mild cold-like symptoms to flu-like discomforts.

A few more notable strains, including SARS-CoV-2 (responsible for COVID-19), and those responsible for severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), can cause death in humans. The cause of death is complex, though is typically the result of heightened immune responses causing damage in multiple systems throughout the body.

Why is it called a coronavirus?

First described in detail in the 1960s, the coronavirus gets its name from a distinctive corona or 'crown' of sugary-proteins that projects from the envelope surrounding the particle. Encoding the virus's make-up is the longest genome of any RNA-based virus – a single strand of nucleic acid roughly 26,000 to 32,000 bases long.

There are four known genuses in the family, named Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and Deltacoronavirus. The first two only infect mammals, including bats, pigs, cats, and humans. Gammacoronavirus mostly infects birds such as poultry, while Deltacoronavirus can infect both birds and mammals.

What are the symptoms of a coronavirus?

Coronaviruses can give rise to a variety of symptoms in different animals. In a high percentage of cases, infection causes no symptoms at all. These individuals can still easily spread the virus without knowing they're infected.

While some strains cause diarrhoea in pigs and in turkeys, in humans infections are usually compared to a bad cold, causing mild to moderate upper respiratory problems such as a runny nose and sore throat.

There are a handful of lethal exceptions, which have had a devastating impact on livestock and human health around the globe. Symptoms in these cases tend to start with a sore throat and fever.

In the specific case of the novel coronavirus COVID-19, most of those infected experience a fever within five days of being infected, followed by a cough. This differs to a flu, which tends to start with a cough.

Severe cases can require hospitalisation from respiratory distress within about a week of the first symptoms showing. Where symptoms continue to worsen, death can follow within two weeks to nearly two months, depending on prognosis and medical care.

What is COVID-19?

COVID-19 is the illness that presents on being infected by a deadly coronavirus called SARS-CoV-2.

This SARS-related virus was first identified in the Chinese city of Wuhan in late 2019. Snakes were originally suspected as a potential source for the outbreak, though other experts have deemed this unlikely and proposed bats as a reservoir instead. Pangolins have been implicated as a potential link in the transfer chain.

As of April 2020, the search for the animal origin of COVID-19 is ongoing.

At the time of writing, numbers of infected are still on the rise, with a mortality rate that varies significantly around the world from less than one to more than 10 percent.

The SARS-CoV-2 pandemic has caused significant disruptions to economies and social activities around the globe throughout 2020. Treatments and protective therapies are currently in development, with programs expected to begin vaccinations in the US by the start of 2021.

What is SARS?

SARS was first recognised as a distinct strain of coronavirus in 2003. The source of the virus has never been clear, though the first human infections can be traced back to the Chinese province of Guangdong in 2002.

The virus then became a pandemic, causing more than 8,000 infections of an influenza-like disease in 26 countries with close to 800 deaths.

What is MERS?

MERS was first identified in Saudi Arabia in 2012 in people displaying symptoms of fever, cough, shortness of breath and occasionally gastrointestinal problems such as diarrhoea. An animal source for the virus has never been officially confirmed, though evidence points to dromedary camels as a potential reservoir of infection.

The World Health Organisation has identified around 2,500 cases of infection in 27 countries since initial outbreaks, resulting in nearly 860 deaths.

All articles are determined by fact checkers to be correct and relevant at the time of publishing. Information published on the coronavirus during the 2020 COVID-19 pandemic may be updated frequently to reflect the dynamic nature of current understanding.