In November 2019, little was known about a mysterious disease that was first identified in the Chinese city of Wuhan.
More than 100m cases have now been diagnosed worldwide, and 2.1m people have died after contracting the virus.
But what have we learned since the first pandemic began?
Coronavirus (Covid-19) is an infectious disease caused by a recently discovered coronavirus called SARS-CoV-2.
The World Health Organization (WHO) first learned about this new virus on December 31, 2019, following a report of a collection of cases of viral virus in Wuhan, China.
Covid-19 is believed to have a zoonotic origin, meaning that it was active in animals before being sent to humans.
It was thought early in the pandemic that the revolution may have started in the Huanan Seafood Wholesale Market, which sold live animals.
Earlier this month, China accused Boris Johnson of “groundless conquest” after the UK Prime Minister suggested that coronavirus could have spread from people grinding pangolins’ scales.
Mr Johnson said the virus came from bats or pangolins, and that the pandemic was “the result of an imbalance in human relationships with the natural world”.
A global team of researchers from WHO arrived in Wuhan in mid-January to investigate the origins of the virus.
The most common symptoms of the virus are fever, dry cough and fatigue.
Symptoms of severe Covid – 19 disease include shortness of breath, loss of appetite, upset, persistent pain or pressure in the chest, and temperatures above 38C.
About 80% of people recover from the illness without needing hospital treatment, around 15% become very ill and need oxygen and 5% become seriously ill and need care severe, according to the WHO.
People aged 60 or over, and those with underlying medical problems such as high blood pressure, heart and lung problems, diabetes, obesity or cancer, are at greater risk of developing a serious illness.
Care includes oxygenation for critically ill patients and those at risk of severe disease, and more advanced respiratory support such as ventilation can be provided for critically ill patients.
Tocilizumab and sarilumab – commonly used for the treatment of rheumatoid arthritis – have been found to “significantly” reduce the risk of death as well as spend time in hospital for up to 10 days.
Results from various clinical trials showed that both drugs reduced the overall mortality risk by 8.5 percentage points when given to patients within a day of admission to intensive care with a corticosteroid, dexamethasone width.
The cheap steroid dexamethasone was declared a major breakthrough in June last year because a study suggested it was the first drug to reduce coronavirus death.
From May last year, doctors were able to prescribe the drug remdesivir, which has been proven to shorten the recovery period, for those with severe Covid-19 disease.
In early December, the UK became the first country in the world to approve the coronavirus vaccine from Pfizer and BioNTech, before approving a vaccine from Oxford University and AstraZeneca later this month.
The EU has approved vaccines from Moderna and Pfizer, and the AztraZeneca vaccine is expected to be approved this week.
Long Covid, also known as post-Covid syndrome, is used to describe the effects of Covid-19 that persist for weeks or months longer than the original illness.
The latest official guidance from the National Institute for Health and Care Excellence (Nice) long defines Covid as “signs and symptoms that develop during or after a Covid-19-compatible disease that persists more than 12 weeks and not explained by other judgments ”.
The condition is associated with a range of symptoms, from fatigue and shortness of breath to anxiety and depression.