The World Health Organisation has given warning that a new strain of the coronavirus could be passed on between people in close contact.
The warning comes after reports on Sunday that a man who contracted a deadly new SARS-like virus after sharing a hospital ward with France's first victim, had been moved to intensive care following a deterioration in his condition.
The first victim, also being treated at the University Hospital in the northern city of Lille, was said to be in a "very serious but stable" condition as health officials attempted to play down public concern over two cases that are attracting intense media coverage.
The latest French victim shared a hospital room in April at Valenciennes hospital in northern France with a 65-year-old man for three days before the latter was diagnosed with the virus, which it is thought he contracted while on holiday in the UAE emirate of Dubai last month.
"The first patient [infected by the novel coronavirus] is in a stable but worrying situation. The situation of the second patient deteriorated and that justified his transfer to intensive care," Marisol Touraine, France's health minister, said on Sunday.
Thirty-nine people who came into contact with the second patient are now being checked by authorities for the virus.
The virus, known as nCoV-EMC, is a cousin of Severe Acute Respiratory Syndrome (SARS), which killed nearly 800 people in the East Asia in 2002-03.
The new virus is known to have killed at least 18 people, mostly in Saudi Arabia.