Airborne Spread of Virus: WHO reviews report urging new guidance

The World Health Organization (WHO) is reviewing a report urging it to update guidance on the novel coronavirus after more than 200 scientists, in a letter to the health agency, outlined evidence the virus can spread in tiny airborne particles.

The WHO says SARS-CoV-2, the virus that causes Covid-19, spreads primarily through small droplets expelled from the nose and mouth of an infected person that quickly sink to the ground.

But in an open letter to the Geneva-based agency, published on Monday in the Clinical Infectious Diseases journal, 239 scientists in 32 countries outlined evidence that they say shows floating virus particles can infect people who breathe them in.

Because those smaller particles can linger in the air, the scientists are urging WHO to update its guidance.

"We are aware of the article and are reviewing its contents with our technical experts," WHO spokesman Tarik Jasarevic said on Monday in an email.

How frequently the coronavirus can spread by the airborne or aerosol route - as opposed to by larger droplets in coughs and sneezes - is not clear.

Any change in the WHO's assessment of risk of transmission could affect its current advice on keeping 1-metre (3.3 feet) of physical distancing. Governments, which rely on the agency for guidance policy, may also have to adjust public health measures aimed at curbing the spread of the virus.

Although the WHO has said it is considering aerosols as a possible route of transmission, it has yet to be convinced that the evidence warrants a change in guidance.

Dr. Michael Osterholm, an infectious disease expert at the University of Minnesota, said the WHO has long been reluctant to acknowledge aerosol transmission of influenza, "in spite of compelling data," and sees the current controversy as part of that simmering debate.

"I think the frustration level has finally boiled over with regard to the role that airborne transmission plays in diseases like influenza and SARS-CoV-2," Osterholm said.

Professor Babak Javid, an infectious disease consultant at Cambridge University Hospitals, said airborne transmission of the virus is possible and even likely, but said evidence over how long the virus stays airborne is lacking.

If it can hang in the air for long periods of time, even after an infected person leaves that space, that could affect the measures healthcare workers and others take to protect themselves.

WHO guidance to health workers, dated June 29, says SARS-CoV-2 is primarily transmitted through respiratory droplets and on surfaces, reports Reuters.

But airborne transmission is possible in some circumstances, such as when performing intubation and aerosol-generating procedures, the WHO says. They advise medical workers performing such procedures to wear heavy duty N95 respiratory masks and other protective equipment in an adequately ventilated room.

Dr. William Hanage, an epidemiologist at the Harvard T H Chan School of Public Health, said the report under review at the WHO "makes many reasonable points about the evidence that this mode of transmission can happen, and they should be taken seriously."

But how often airborne transmission happens, which is unknown, also matters.

BUBONIC PLAGUE

WHO said yesterday it was monitoring a case of bubonic plague in China after being notified by the authorities in Beijing.

A herdsman in China's northern Inner Mongolia region was confirmed at the weekend to have the bubonic plague.

Two other cases were confirmed in Khovd province in neighbouring Mongolia last week involving brothers who had eaten marmot meat, China's state news agency Xinhua said.

"Bubonic plague has been with us and is always with us, for centuries," WHO spokeswoman Margaret Harris told reporters at a virtual briefing.

"We are looking at the case numbers in China. It's being well managed. At the moment, we are not considering it high-risk but we're watching it, monitoring it carefully."

She said the WHO was working in partnership with the Chinese and Mongolian authorities.

The UN health agency said it was notified by China on July 6 of a case of bubonic plague in Inner Mongolia, reports AFP.

"Plague is rare, typically found in selected geographical areas across the globe where it is still endemic," the agency said, adding that sporadic cases of plague have been reported in China over the last decade.

"Bubonic plague is the most common form and is transmitted between animals and humans through the bite of infected fleas and direct contact with carcases of infected small animals. It is not easily transmitted between people."

Though the highly-contagious plague is rare in China and can be treated, at least five people have died from it since 2014, according to China's National Health Commission.

The man infected in Inner Mongolia was in stable condition at a hospital in Bayannur, the city health commission said in a statement.

Xinhua said that in neighbouring Mongolia, another suspected case, involving a 15-year-old boy who had a fever after eating a marmot hunted by a dog, was reported on Monday.