Quit Victoria says there is "emerging evidence" that people who smoke are likely to be more susceptible to catching COVID-19 and being affected by the illness.

Two leading respiratory researchers this week highlighted that smokers are at a higher risk because their habit curbs the immune system and causes lung problems, the organisation says.

That means people who smoke need to extra cautious right now, Quit Victoria director Dr Sarah White says.

"Please don't share cigarettes, water pipes or e-cigarettes and be very aware that the hand-to-mouth action of smoking and vaping means you are frequently bringing your hands into close contact with your face," she said on Friday.

"Practising good hand hygiene is a must."

She said now was a "good time to make a quit attempt".

"You can make self-isolation and your friends and family around you - physically or online - work for you," Dr White said, adding people can call the Quitline on 13 7848 for help.

Quitline has experienced a slight increase in callers wanting to quit, with almost 100 per cent of them telling counsellors they were worried about COVID-19.

VicHealth chief executive Dr Sandro Demaio said quitting improved people's ability to transport and utilise oxygen, their respiratory function and the strength of their immune system.

"Quitting now gives you a better chance of recovering from coronavirus, while in the longer term you'll have the opportunity to enjoy better health overall," Dr Demaio said.

Australian Associated Press