COVID-19, commonly referred to as coronavirus, emerged from its epicentre in Wuhan, China, in January
Within two months, it had spread to more than 140 countries on six continents and been classified by the World Health Organisation (WHO) as a global pandemic.
What is a coronavirus?
Coronaviruses are zoonotic, meaning that they are transferred from animals to humans. Others you might have heard of include Severe Acute Respiratory Syndrome (SARS) - which was transmitted from cats to humans - and Middle East Respiratory Syndrome (MERS), which was transmitted from camels.
Scientists are already aware of several coronaviruses circulating in animals that have not yet been passed to humans. COVID-19, meanwhile, is a 'novel' coronavirus, meaning it is a new strain and has not been previously identified in humans.
The coronavirus is named for the fact the scientists that first looked at the virus under a microscope (back in 1968) thought that it resembled a "solar crown", the ring of gas that surrounds a sun.
Where did the virus come from?
The virus originated in Wuhan, a city of 11 million people in the central Chinese province of Hubei and most of the more than 3,300 deaths officially communicated by the country have been in the province.
It is believed that the virus was transmitted via bats and that its epicentre was the Wuhan Huanan Seafood Wholesale Market. But the WHO has also suggested that the virus could have originated in pangolins, also known as scaly anteaters, an endangered species that is used in Chinese medicine.
Genetically, the new virus is 80% similar to SARS, which spread rapidly in 2002 and 2003 and killed 800 people.
What are the symptoms?
This new virus can, in more severe cases, cause pneumonia, severe acute respiratory syndrome and kidney failure.
Common signs of the infection include respiratory symptoms, fever, cough, shortness of breath and breathing difficulties.
One of the problems with the coronavirus is that the symptoms can be mild, especially in younger, healthier people, similar in some cases to the common cold or seasonal flu. The WHO estimated for instance that 80% of people will experience mild symptoms.
As a result, some health authorities have urged people with symptoms not to go to their GP or an emergency room and instead to self-isolate for 14 days.
Another problem is that in some people - particularly children - the disease can be asymptomatic, but is still contagious.
Lastly, the disease is most deadly in people over 70 and those who have existing health conditions.
How is the virus transmitted?
The disease can be spread from person to person through moisture from the nose or mouth, which is passed on when an infected person coughs or sneezes.
That is why health authorities have warned people to stay at least a metre away from anyone who is sick, and advised those who are sick to cover their mouths when they cough or sneeze.
Droplets of moisture land on objects and surfaces around the person and are passed on when another person touches those surfaces or objects and then touches their nose or mouth.
What measures are countries taking?
In the early days of the virus, China put three cities -Wuhan, Huanggang and Ezhou - on lockdown: stopping outbound travel in an effort to contain the virus.
Italy was the first European country to impose similar restrictions, first in northern regions — the epicentre fo the outbreak in Itay — and later extending them to the rest of the country.
Most of the other EU member states followed suit by first closing school and universities and then shutting down all non-essential shops and public places. Gatherings became progressively more restrictive with Germany even banning gatherings of more than two people.
Is social distancing effective?
Most European counties initially tabled 15-days lockdowns but ended up prolonging them to flatten the curve.
It is not known for how long a patient is contagious. Chinese studies have shown that the virus can be detected in patients (and therefore potentially transmitted) for 8 to 37 days, with an average of 20 days.
Researchers at the Imperial College in London have found that social distancing measures could halve the number of deaths in Great Britain from 510,000 in an “unmitigated epidemic” (without social distancing strategies in place) to about 250,000 people if they are in place and everyone is able to be treated.
But it's unlikely everyone could be treated, because even with these strategies in place, hospitals will overflow, the researchers said.
How long will it last?
It is the million-dollar question. The number of cases in China initially surged, then see-sawed and just as it was stabilising there towards the end of February, reported cases and deaths started going up very quickly in Europe.
By mid-March, as Europe continued to struggle to contain the spread of the virus, it was the US's turn to start seeing the number of cases shoot up exponentially.
US cases quickly overtook Italy and China with the country becoming the first to report more than 100,000 confirmed cases.
Most estimates suggest that a vaccine for coronavirus is at least a year away, although scientists in Israel recently said that they were 'a few weeks' from developing one.