The coronavirus, which originated in Wuhan, has affected more than 20,000 people in China and killed at least 425 people. In Singapore, there is now local transmission, as four of the six new cases announced on Tuesday (Feb 4) did not travel to China. In total, there are now 24 confirmed cases in Singapore, and the Government has warned that there could be broader community spread.

Senior health correspondent Joyce Teo asked two infectious disease experts for their take on the latest developments in this outbreak. They are Professor Wang Lin Fa, the director of the emerging infectious disease programme at Duke-NUS Medical School, and Associate Professor Hsu Li Yang, the programme head (infectious diseases) at the NUS Saw Swee Hock School of Public Health.

1. Can you be infected with the coronavirus just by touching a doorknob?

A recent report said that the coronavirus has been found on a doorknob in the house of an infected person.

Experts have said this virus is transmitted mostly via droplets, and there can be contact transmission when these droplets land on a surface and one then picks up the infection from touching the surface. Prof Wang said that he personally thinks the risk of contact transmission is higher than that of direct droplet transmission.

"You have to be very unlucky to get it from the droplets in the air; it means that the person coughed directly at your face, or very near you, or if an infected person coughed in the lift about 30 seconds before you went in," he said.

The risk of infection in Singapore is considered very low but for ordinary people who want to protect themselves, the first thing they can do is to avoid crowded places.

"And if you really have to go out, the lifts and the public toilets, these are the places where I would be very, very careful about touching any surfaces to not risk a coronavirus infection," said Prof Wang.

If someone used the lift 30 seconds or a minute before you, there's a "low chance" of you getting an infection from breathing in the air but a much higher chance of getting it from contact, that is, from touching the lift buttons.

"Everybody's wearing a mask but they are not doing anything to protect their hands," he said. "The lift is the most dangerous place because it is an enclosed space, and everybody has to touch the button to go up or down, or to close the door."

One tip he's learnt from social media is to use a pen to press the lift buttons. Get one with a cap and remove the ink cartridge before using it. After using it, cap it and put it in your bag.

Cars are also enclosed spaces. Prof Wang said that people can use a hand sanitiser after getting in and out of a car or cab. Drivers can air the vehicle after dropping a passenger off.

"If a previous passenger is infected and let's say, he coughed in the car five minutes ago, and you then open the windows for two to three minutes, you should get enough circulation to clear the air because the droplets cannot stay in the air for so long if it's a fully ventilated environment."

2. Is faecal transmission possible?

Recent reports have discussed this. Prof Wang said this is possible and said that during the Sars outbreak in Hong Kong in 2003, more than 300 people at an apartment complex called Amoy Gardens reportedly caught the disease through the sewage system. It was reported then that the moist conditions in the bathrooms in Amoy Gardens had allowed water droplets containing the virus to form. Bathroom extractor fans then sucked the virus into the flats, spreading it. Singapore has a different sewage system.

At the complex, Sars was also apparently spread through person-to-person contact and in common areas, such as lifts, lobbies and staircases.

3. Can younger people be easily infected?

There have been confirmed cases of people in their 30s and 40s; the first person to die from the coronavirus in Hong Kong is a 39-year-old who had travelled to Wuhan. He had an underlying illness.

Prof Wang said some 80 per cent to 90 per cent of the severe or fatal cases are either the elderly or those with underlying medical conditions.

What these people - the elderly and those with serious underlying medical conditions - can do is to avoid crowded places and stay at home as much as possible, he said.

Prof Wang, who is 59, said he has been on a self-imposed home quarantine after returning from Wuhan in mid-January.

4. Is this likely going to be a pandemic?

Experts have been quoted in media reports saying that the coronavirus outbreak looks increasingly like a pandemic. A pandemic is when a disease is prevalent in a whole country or the world.

"We do not know for sure yet. The 2019-nCoV is much harder to contain compared with Sars, but China has instituted outbreak control measures on a scale that has dwarfed all other efforts in the past," said Prof Hsu, using the scientific name for the coronavirus.

"Even if the epidemic is eventually brought under control, it is likely that this will take a far longer period than Sars (which was nine months). If we have a commercially available and effective vaccine in over a year, that will be most helpful."

5. Will this coronavirus grow weaker as the weather grows hotter?

There is talk that the virus spreads more easily in cold weather.

Prof Hsu said that cold, dry air does result in better spread of the flu virus and human coronaviruses, which is why the influenza season typically coincides with winter every year.

"We do not know enough about the new virus to be sure, but it is plausible that the same is true," he said.

Nevertheless, he added: "Singapore is in the tropics and does not have winter, and we also have influenza all year round."