The World Health Organisation says it appears increasingly likely that a new strain of coronavirus, which can cause pneumonia and kidney failure, can be passed by close personal contact.
The new strain is similar to the virus that caused severe acute respiratory syndrome or SARS.
France has confirmed a second case of the deadly new virus.
A hospital roommate of the 65-year-old man who initially contracted the virus tested positive for the illness.
The second patient's condition has deteriorated, requiring treatment in intensive care, Health Minister Marisol Touraine said at a news conference.
The minister added that the first patient is "in a stable but worrisome situation".
Ms Touraine said pamphlets listing precautionary measures and potential signs of illness will be available at French airports for travellers, especially those visiting the Arabian Peninsula.
The novel coronavirus has killed 18 people since being identified last year.
More than 30 confirmed cases were reported to the WHO since September 2012.
Most of those infected since the virus was identified had travelled to Qatar, Saudi Arabia, Jordan or Pakistan.
There also have been cases in Britain and Germany.
The novel coronavirus is related to SARS, which killed some 800 people in a global epidemic in 2003, and belongs to a family of viruses that most often causes the common cold.
The virus is most closely related to a bat virus and scientists are also considering whether bats or animals such as camels or goats are a possible source of infection.
Scientists are also considering whether fruit contaminated by animal droppings may have spread the virus.
Officials are trying to track down all people who had contact with the second patient in France as well as all those who travelled to Dubai on an organised tour with the man initially diagnosed with the virus.
"Professionals, doctors, consider that there is no need for excessive worry, but once again we should be vigilant," the health minister said. "I am repeating: Nothing is being left to chance."
