GENEVA — The World Health Organization today said that medical masks should be prioritized for health workers, but it opened the door to greater public use of homemade masks or other mouth coverings as a way to reduce the spread of the coronavirus.

A senior WHO official told reporters there was some possibility of airborne transmission of the virus that has now infected over 1 million people and killed 50,000 people worldwide since emerging in China last December.

But the main driver of the pandemic was still believed to be sick people with symptoms who were coughing and sneezing and contaminating surfaces or other people.

"We must preserve medical surgical respirator masks for our frontline workers. But the idea of using respiratory coverings or mouth coverings to prevent coughing or sneezing projecting disease into the environment and towards others ... that in itself is not a bad idea," Dr. Mike Ryan, the WHO's top emergencies expert, told a news conference.

Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Disease who is top US infectious disease official, said on Friday that Americans should cover their face if they have to go in public, but they should still stay isolated as much as possible.

Ryan acknowledged a "very important and healthy debate" on the wearing of masks.

He said that if used, they should be part of a comprehensive strategy and would not negate the need for hand washing and social distancing.

"So we can certainly see circumstances in which the use of masks, both homemade or cloth masks, at community level may help in an overall comprehensive response to this disease," he said.

Ryan, citing data from Italy, said that there did not appear to be a link between people taking drugs against hypertension known as ace inhibitors and getting the disease or developing severe disease. — SPA