New York Times
June 16, 2020

Professor Don Milton's expertise related to the airborne transmission of viruses was again referenced by the New York Times in a story about the World Health Organization's June 8 statement that transmission of the coronavirus by people without symptoms is “very rare.”

Following concerted pushback from researchers, W.H.O. officials walked back the claim, saying it was a “misunderstanding.”

Scientsts, including Dr. Milton, claim that the W.H.O. defines airborne transmission too narrowly. Airborne transmission also includes the possibility that the virus is aloft for shorter distances, then inhaled.

“They have a very early 20th century, very unsophisticated view of what aerosols and airborne transmission are,” said Dr. Don Milton, an expert on public health aerobiology at the University of Maryland.

Up until the 1950s, Dr. Milton said, tuberculosis was thought to be spread by prolonged close contact. “We now know that it’s only transmitted by aerosols,” he said.

The WHO had delayed endorsing masks for the general public until June 5, claiming there was too little evidence that they prevented transmission of the virus. Virtually all scientists and governments have been recommending masks for months.

All of the experts interviewed for the New York Times article said it was not that the W.H.O. is wrong on all counts, but that given the implications of its statements, it should be more cautious in concluding that transmission by air or by people without symptoms is not significant.

“We don’t know,” Dr. Milton said. “But they also don’t know.”

Dr. Milton is currently conducting a research study aimed at gathering new evidence related to how SARS-CoV-2, the virus that causes Covid-19, may spread by air.

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