Dr Li Wenliang contracted the virus while working at Wuhan Central Hospital

There have now been more than 40,000 cases of coronavirus, which has been declared a global health emergency. The disease has spread to many countries, including the UK.

The answers to a selection of readers' questions about the new virus are below.

Once you've had coronavirus, will you then be immune? Denise Mitchell, Bicester

When people recover from an infection their body is left with some memory of how to fight it should they encounter it again. This immunity is not always long-lasting or totally efficient, however, and can decrease over time. It is not known how long immunity might last after being infected.

What are differences between coronavirus and flu? Brent Starr, Gresham, Oregon, US

Coronavirus and flu share many similar symptoms, making it difficult to diagnose without a test. The main coronavirus symptoms to look out for are fever and a cough. Flu often has other symptoms too, such as aching muscles and a sore throat, while people with coronavirus may feel short of breath.

Anyone who suspects they may have caught coronavirus, because they have had close contact with another infected person or have travelled to an area where the virus is circulating, should talk to their doctor.

Can coronavirus be transmitted sexually? David Cheong, Singapore

It is not clear yet whether this is a route of transmission that we should be concerned about. Currently, it is coughs and sneezes from an infected person that are thought to be the main source of spread.

How come a Chinese doctor in his mid-30s has died from this 'flu-like' virus? Jeffrey

It might be that Dr Li had other, unreported, health conditions that put him at greater risk. Or he may have been exposed to a higher initial dose of the virus that meant he developed more severe symptoms. But it is also worth remembering that seasonal flu mostly kills the young and old, but can kill people in the prime of their life.

Is a face mask useful against the virus and how often does it have to be replaced? Tom Lim, Bali, Indonesia

There is very little evidence that wearing face masks makes a difference. Experts say good hygiene - such as regularly washing your hands and certainly before putting them near your mouth - is vastly more effective.

What is the incubation period for the coronavirus? - Gillian Gibs

The World Health Organization says the incubation period, which is the time before symptoms appear, ranges from two to 10 days.

These estimates will be narrowed down as more data becomes available.

Do people who have contracted coronavirus return to full health? - Chris Stepney, Milton Keynes

Yes. Many of those who contract coronavirus will experience only mild symptoms, and most people are expected to make a full recovery.

However, it can pose a particular risk for elderly people and those with pre-existing problems like diabetes or cancer, or weak immune systems.

An expert at China's National Health Commission has said that it can take a week to recover from mild coronavirus symptoms.

Can the coronavirus be transferred through items bought from Wuhan and posted to UK? - Stefan

There is no evidence this is a risk. Some diseases - including the coronavirus that causes Sars - can spread through surfaces contaminated by people coughing or sneezing on them.

It has not been shown this new coronavirus can do that. Even if it could, there would still be questions about whether international shipping would be a major problem.

Cold viruses tend to survive less than 24 hours outside the human body although norovirus (a severe stomach bug) can last months outside the body.

The most reassuring fact so far is that cases seem to require close contact with another person - say, a family member or healthcare worker - in order to spread.

Is there any reason such viruses are emerging more from China? - Gautam

Yes - large populations of people living in close proximity to animals.

This coronavirus almost certainly came from an animal source, with one suggestion being snakes. Sars, another coronavirus that originated in China, came from bats and the civet cat.

The early cases of this new infection were traced to the South China Seafood Wholesale Market. Live wild animals were also sold including chickens, bats and snakes.

Is it possible to vaccinate in order to prevent this respiratory illness? - Hans Friedrich

At the moment, there is no vaccine that can protect people against this type of coronavirus, but researchers are looking to develop one.

It is a new strain that hasn't been seen in humans before, which means doctors still have lots to learn about it. BBC