WHO stance on virus transmission at issue

SEATTLE — Six months into a pandemic that has killed more than half a million people, more than 200 scientists from around the world are challenging the official view of how the coronavirus spreads.

The World Health Organization and the U.S. Centers for Disease Control and Prevention maintain that you have to worry about only two types of transmission: inhaling respiratory droplets from an infected person near youor — less common

— touching a contaminated surface and then your face.

But other experts contend that particles known as aerosols — microscopic respiratory droplets — can hang in the air for long periods and float dozens of feet, making poorly ventilated spaces dangerous, even when people stay 6 feet apart.

“We are 100 percent sure about this,” said Lidia Morawska, a professor of atmospheric sciences and environmental engineering at Queensland University of Technology in Brisbane, Australia. She makes the case in an open letter to the WHO. A total of 239 researchers from 32 countries signed the letter, which is set to be published next week.

WHO officials have acknowledged that the virus can be transmitted through aerosols but say that occurs only during medical procedures such as intubation. CDC officials did not respond to multiple requests for comment.

Dr. Benedetta Allegranzi, a top WHO expert on infection prevention and control, said that Morawska and her group presented theories based on laboratory experiments rather than evidence from the field.

“We value and respect their opinions and contributions to this debate,” Allegranzi wrote in an email. But a large majority of a group of more than 30 international experts advising the WHO has “not judged the existing evidence sufficiently convincing to consider airborne transmission as having an important role in COVID-19 spread.” She added that such transmission “would have resulted in many more cases and even more rapid spread of the virus.”