Smokers are up to 50 per cent more likely to become seriously ill or die from Covid-19, the head of the World Health Organisation said.
On Friday, Dr Tedros Adhanom Ghebreyesus discussed a developing area of research into the effects of Covid-19.
The UN health agency said smokers were more likely to have difficulty fighting off the disease because of damage the habit causes to their lungs.
“Smokers have up to a 50 per cent higher risk of developing severe disease and death from Covid-19,” Dr Tedros said as part of a message to mark World No Tobacco Day on May 31.
“Quitting is the best thing smokers can do to lower their risk from this coronavirus, as well as the risk of developing cancers, heart disease and respiratory illnesses.”
In January, a UK study of 2.4 million people found that smokers are more likely to report symptoms such as coughs, fever and breathlessness after contracting Covid-19.
The researchers said efforts to reduce smoking should be part of the public health response to the pandemic.
Aside from reducing the risk from the disease, it would ease the burden on hospitals struggling to treat patients for other illnesses, they said.
Warnings over infection risk from smoking
The link between smoking and Covid-19 has yet to be fully understood, and health authorities in the UK say the evidence in the field is “mixed and developing”.
The WHO suggests smokers may also be at higher risk of becoming infected through the mouth while smoking or using other tobacco products.
Other studies appear to show that smokers could be less likely to contract the disease, but the WHO played down such findings and described them as unproven when they were reported last year.
Public Health England says smokers should avoid sharing cigarettes to help reduce the risk of passing on the virus.
It says that sharing mouthpieces from shisha pipes "greatly increases the risk of spreading Covid-19".
The WHO announced on Friday that smoking rates in Europe remain high and are unlikely to drop without government action.
About 26 per cent of adults smoke in Europe and this is only expected to fall by about 2 per cent by 2025, the WHO said.
In France, health authority Sante Publique reported that a years-long downward trend in smoking ended in 2020.
Blaming a “social crisis context” in a year marked by the pandemic, the group said fewer smokers attempted to quit during 2020.