Covid-19 is a strain of coronavirus that causes respiratory issues and can be fatal.
Coronaviruses (CoV) are a large family of viruses causing illness ranging from the common cold to more severe diseases such as Middle East Respiratory Syndrome (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS-CoV).
The virus originated in Wuhan, China but has gone on to infect hundreds of thousands worldwide in more than 200 countries.
Across the globe at least 40,000 people have died after testing positive for Covid-19.
The World Heath Organisation (WHO) has classed the outbreak as a pandemic.
A pandemic - according the the WHO - is the worldwide spread of a new disease, as opposed to an epidemic, which is a disease contained within one country.
"Pandemic is not a word to use lightly or carelessly," WHO's Director-General Tedros Adhanom Ghebreyesus said.
"It is a word that, if misused, can cause unreasonable fear, or unjustified acceptance that the fight is over, leading to unnecessary suffering and death."
- What are the symptoms of Covid-19?
According to the NHS, the symptoms of coronavirus are a new and continuous cough, a high temperature and shortness of breath.
Since these symptoms are those for a variety of illnesses, such as commons colds and flu, if you have them you do not necessarily have Covid-19.
Public Health England (PHE) said the virus may progress to more severe illnesses, such as pneumonia.
Older patients and those with underlying health conditions are more likely to progress to severe disease.
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- Are there any other symptoms?
While the main symptoms to watch out for, according to PHE, are a cough and a fever, recent scientific research suggests a loss of smell could be another indicator.
Researchers from King’s College London say a loss of smell and taste may be the best way to tell whether you have Covid-19.
Almost 60% of people who tested positive for coronavirus reported loss of smell and taste, compared with 18% of those who tested negative, analysis of data from their specially-created app found.
The British Association of Otorhinolaryngology (ENT UK) released a statement saying they have circulated intelligence to PHE regarding anosmia - the loss of the sense of smell.
"There is already good evidence from South Korea, China and Italy that significant numbers of patients with proven COVID-19 infection have developed anosmia/hyposmia," ENT UK said.
"In Germany it is reported that more than two in three confirmed cases have anosmia.
"In South Korea, where testing has been more widespread, 30 per cent of patients testing positive have had anosmia as their major presenting symptom in otherwise mild cases."
PHE say 'there is a range of symptoms" but do not specify a loss of smell.
On the question of symptoms, NHS England's National Medical Director Steve Powis said: "The two commonest are by far cough and a fever and that is exactly why they are the two symptoms that we are asking people to self-isolate if they get those symptoms."
- What should you do if you think you may have Covid-19?
Many of those infected with coronavirus will develop only mild to moderate symptoms.
Shelley Folkes a locum nurse told ITV News "plenty of rest, lots and lots of fluid" are needed as well as "simple paracetamol to combat a fever."
Nichola Mazur, an NHS nurse who works on the frontline, said most who develop symptoms will not need to go to hospital.
"No, if you do have symptoms you don't go into hospital - if you do have the virus this can then spread to other people," said Ms Mazur.
"For most people, you will recover at home without the need for any medical intervention."
Ms Folkes added: "If your symptoms become unmanageable then there is the online 111 assessment tool that will guide you through an assessment to tell you which pathway you need to take at the moment.
"Obviously, if your symptoms become very severe like extreme shortness of breath or reduced conscious level then you will need to call 999 and the ambulance service will assess you over the phone."
- Treatment for coronavirus
There is currently no vaccine for Covid-19, though a number of potential vaccines are in development.
The virus attacks and kills two specific types of cells in our lungs, known as the goblet and ciliated cells.
The cells are vital to keeping the lungs healthy, losing them can lead to potentially lethal pneumonia. In some cases, the virus causes the immune system to go into overdrive, attacking the lungs themselves.
The virus can also attack the kidneys - and, in some cases, the blood vessels and circulation.
Antibiotics do not help, as they do not work against viruses.
Treatment instead aims to relieve the symptoms while your body fights the illness.
You'll need to stay in isolation away from other people until you've recovered.
- How is Covid-19 spread?
Coronavirus can spread from person-to-person in close proximity, similar to other respiratory illnesses, such as the flu.
Droplets of bodily fluids - such as saliva or mucus - from an infected person are dispersed in the air or on surfaces by coughing or sneezing.
These droplets can come into direct contact with other people or can infect those who pick them up by touching infected surfaces and then their face.
According to scientists, coughs and sneezes can travel several feet and stay suspended in the air for up to 10 minutes.
It is not yet known how long the virus can survive outside a host but, in other viruses, it ranges from a few hours to months.
Transmission is of particular concern on transport and in public places, where droplets containing the coronavirus could pass between people or via surfaces.
The incubation period of the coronavirus - the length of time before symptoms appear - is between one and 14 days.
It is thought Covid-19 can be transmitted before symptoms appear, making it easy to spread.
- Who is particularly vulnerable?
Around 1.5 million people across England have been warned to stay at home for at least 12 weeks to avoid being hospitalised by the virus.
A raft of new measures on shielding and protecting to help the nation's most vulnerable have been announced by the government.
People who fall into the extremely vulnerable group include: organ transplant recipients, people with specific cancers, severe respiratory conditions, rare diseases and those on immunosuppression therapies.
Women who are pregnant with significant heart disease are also included on the list.
For a full breakdown, click here.
- What precautions should we take?
You can do the following to help stop the spread of any virus, not just coronavirus:
- Cover your mouth and nose with a tissue or your sleeve (not your hands) when you cough or sneeze and immediately bin used tissues
- Wash your hands with soap and water often – use hand sanitiser gel if soap and water are not available
- Try to avoid close contact with people who are unwell
- Don't touch your eyes, nose or mouth if your hands are not clean
- What do I need to do?
Social distancing. This entails the following steps:
- Avoid contact with someone who is displaying symptoms of Covid-19 (remember, these symptoms include high temperature and/or new and continuous cough)
- Avoid non-essential use of public transport when possible
- Work from home, where possible
- Avoid large and small gatherings in public spaces
- Avoid gatherings with friends and family - keep in touch using remote technology such as the phone, internet, and social media
- Use telephone or online services to contact your GP or other essential services
- Where did coronavirus come from?
On December 31 last year, the World Health Organization (WHO) was informed of a cluster of cases of pneumonia of unknown cause in Wuhan City, Hubei Province, China.
On January 12, Covid-19 was identified in samples obtained from cases.
Initial analysis suggested that this was the cause of the outbreak and it is thought to have originated from an illegal wildlife market, possibly from a pangolin (a scaly anteater which is prized in China for its use in traditional medicine).