Former US president Barack Obama called for people to take "common sense precautions" over the coronavirus outbreak -- advising them to follow hand-washing guidelines but not to wear masks.
"Save the masks for health care workers. Let's stay calm, listen to the experts, and follow the science," tweeted Obama, who has kept a low public profile since leaving office in 2017.
He said people should keep track of updates from the Centers for Disease Control and Prevention -- and stay home if they are sick.
The World Health Organisation has said masks, goggles and other protective equipment used by health workers were in short supply due to "rising demand, hoarding and misuse."
The death toll in the US from the virus rose to 11 on Wednesday, as lawmakers in Congress reached a deal to provide more than $8 billion to fight the outbreak.
Nationwide, more than 130 people have so far been infected, with the virus detected in more than a dozen states.