NEW YORK (REUTERS, BLOOMBERG) - Smoking or vaping makes people more vulnerable to suffering severe illness once infected by coronavirus, a spokesman for New York City mayor Bill de Blasio said on Sunday (March 8).

Mr de Blasio told a press conference earlier on Sunday that people who smoke or vape are at higher risk.

"If you are a smoker or a vaper that does make you more vulnerable," he said, urging New Yorkers to seek help in quitting.

"If you are a smoker or a vaper this is a very good time to stop that habit, and we will help you."

Mr de Blasio also said people over the age of 50 and with heart disease, lung disease, cancer, immune system vulnerability or diabetes face increased risks.

New York City has 13 confirmed coronavirus cases, the most recent diagnosed in the Bronx.

"As we continue to see community transmission between people who have no direct connection to travel to one of the affected countries, we are asking New Yorkers to adjust their routines to stem the spread of the virus where they can," Mr de Blasio said.

"We could well be at 100 cases or hundreds of cases over the next two or three weeks," he said, adding that "updates may be not as fine-tuned in real time" as the number of cases grows.

He also urged New Yorkers to help minimise the virus' spread. He suggested avoiding the subway at rush hour by cycling or walking to work, or to stay home and telecommute. International travel has been cancelled for city workers and school students.

"We are asking New Yorkers to adjust their routines to stem the spread of the virus where they can," Mr de Blasio said. "If you feel sick, stay home."