Any lingering thought that the transmission of SARS-CoV-2 does not occur through the air should finally be gone. Two recent cases have hit the nail on the head in the hand hygiene theater.
A recent definitive case of COVID-19 transmission occurred at a quarantine hotel in Hong Kong. Patients A and B had both been double vaccinated and both had negative reverse transcription PCR (RT-PCR) for SARS-CoV-2 within 72 hours of arrival. Patient A arrived from South Africa on November 11, 2021. Patient B arrived from Canada on November 10. Both stayed at the Regal Airport Hotel and their rooms were on the same floor, directly across from each other.
Patient A was asymptomatic but had a positive PCR on November 13. Patient B developed mild symptoms on November 17 and tested positive the next day. None of the other people quarantined on this floor tested positive, nor did the hotel staff.
The viral genomes of these two positive cases differed only by one nucleotide, i.e. minimal variation.
The investigation – including footage from closed-circuit television cameras – showed that none of the patients broke quarantine upon leaving their rooms. No other person entered their rooms and no items were shared by them. The patients only opened their doors to collect trays for their meals and to have RT-PCRs done every 3 days. This test did not take place on the same days.
The survey – published in Emerging infectious diseases – concluded that “airborne transmission through the corridor is the most likely mode of transmission”.
It is also reported that the Hong Kong Health Department said the hallway had “unsatisfactory” airflow. They also noted that the source patient, who had traveled from South Africa, sometimes did not wear a mask when recovering from his meals or wore a mask with a valve.
Yuen Kwok-yung, a leading microbiologist at the University of Hong Kong and expert on COVID-19 policy for the government, called the use of face covers fitted with valves “a little selfish,” according to the South China morning post. He blamed the masks for the transmission.
The government’s Center for Health Protection subsequently banned valve masks and urged the use of surgical masks alone. They say the exhaled air is not filtered by the valve.
Although this is a widely held belief, a recent NIOSH (National Institute of Occupational Health and Safety) study contradicts this idea. The researchers’ results were based on tests of 13 models of filter masks (FFR) from 10 different manufacturers. They found that “FFRs with an exhalation valve provide respiratory protection to the wearer and reduce particulate emissions to levels similar or greater than those provided by surgical masks or fabric face covers.”
What is the probable reason for this surprising discovery? Presumably, this is because surgical masks leak significantly from the sides and valve masks fit more securely. This is also why the current mask recommendation is that if you do not have access to an N95, KN95, FFP or similar, you wear a surgical mask. below a tighter and more adjusted fabric mask.
A second case
A second quarantine case similar to Hong Kong’s occurred last year in New Zealand.
Genomic and epidemiological data helped solve this investigation into the epidemic. Here, too, CCTV has confirmed the absence of a quarantine violation.
Examination of the ventilation showed that the rooms were net positive pressure relative to the hallway, allowing air to enter the hallway from the bedrooms.
Ultimately, nine patients were involved in this outbreak. In one group, “there was a 50-second window between closing the door to patient C’s room and opening the door to patient D and E’s room.”
It was therefore a probable earlier case of aerosol transmission without direct person-to-person contact, which has not received much attention.
Ian Mackay, PhD, is a virologist, educator, and author of the highly informative Virology Down Under blog. Mackay told Medscape, “Australia has seen numerous examples of the virus ‘escaping’ the virus from infected travelers quarantined in a hotel – initially due to a failure in aerosol prevention or a lack of understanding they were the main route of transmission. “
He said: “it has been controlled much better in recent months”.
So why do some experts seem surprised by these findings? After all, almost 20 years ago, a mildly ill doctor with flu-like symptoms went to the Metropole Hotel in Hong Kong to attend a wedding – and it sparked a global epidemic, identified by the sequel like SARS.
Seventeen other guests on this doctor’s floor were subsequently infected. Studies have shown that the rooms all have positive hallway pressure. A guest sparked an outbreak in Toronto after she flew from Hong Kong. Others have spread SARS to Singapore and Vietnam. Mysteriously, no hotel staff was infected, nor were guests on other floors.
The ongoing debate
How SARS spreads is still debated.
The World Health Organization (WHO) says it is an airborne virus that spreads in small droplets. The Centers for Diseases Control and Prevention (CDC) say, “The primary way SARS appears to be spread is through close person-to-person contact … and by droplet spread” and by passive vectors (touching infected objects).
The CDC adds that it is “possible for SARS-CoV to spread” by air.
Recently there was a big epidemic among people who attended a Christmas party at a restaurant in Oslo. It is estimated that at least half of the 120 attendees were infected with the new Omicron variant during the party. Two of the participants had recently returned from South Africa.
According to Reuters, all attendees were vaccinated and tested negative before attending an energy company’s end-of-year party.
The Norwegian Institute of Public Health reports that as of December 8, 2021, 70% of participants had been diagnosed with COVID-19. Most of the reported symptoms developed within 3 days. They expect most to be confirmed as having the Omicron variant.
Notably, over 60 other customers who visited another part of the restaurant that evening, but did not not attending the party, also having COVID.
For more examples supporting airborne transmission of COVID-19, check out this in-depth discussion thread from Jose-Luis Jimenez, PhD, an aerosol expert at the University of Colorado, on how to prevent transmission of the virus:
1/ HOW TO AVOID TRANSMISSION and have #CleanAirHolidays?
Most important: understand and explain clearly that we get infected by breathing infected air (aerosols) exhaled by SOME (not all) the infected
— Prof. Jose-Luis Jimenez (@jljcolorado) November 23, 2021
On February 2, 2021, an editorial in Nature said: “There is too much emphasis on surfaces” and called on the CDC and WHO to update their guidelines.
There are also two revealing tweets from Kimberly Prather, PhD, professor and director of CAICE (Center for Aerosol Impacts on Chemistry of the Environment) at UC San Diego. They show that scientists at the CDC and WHO were set to declare COVID-19 as having airborne transmission in February 2020:
Written by the one and only @DrMikeRyan who is also quoted here as contacting @CDCgov when they posted airborne and then removed it from their web site over a 3 day period in September 2020.https://t.co/h6df4rlyD3 https://t.co/eTjTQr207M
— Kimberly Prather, Ph.D. (@kprather88) October 17, 2021
When asked why the WHO and CDC still deny that COVID-19 is only airborne, Jimenez told Medscape that much of this goes back to some of the teachings of infectious disease transmission, starting with a mistake by public health pioneer Charles Chapin in 1910, who claimed that contact was the primary source of respiratory transmission and droplet transmissions were included as part of contact spread.
Don Milton, MD, DrPH, professor of environmental health at the University of Maryland and expert in respiratory virus aerobiology, also traced the origin of the misunderstanding to Chapin.
“There is a deeply held belief in most infectious disease professionals that if you use the word ‘airborne’ you will scare people and then they will panic and do nothing you want them to do,” he told Medscape..
While the CDC now encourages masking indoors if in areas with high COVID transmission, their chatty message has confused the public and raised suspicion.
A lot of people do not understand that they should always mask themselves even if they are fully vaccinated. Too many people believe they have been lied to and do not accept that recommendations change as we learn more. Too much emphasis is still placed on surface disinfection.
It would help if, instead, the CDC and WHO focused on improving ventilation and providing each with high-quality masks, as well as intensive education on how to wear masks. In addition to universal immunization, the CDC and WHO must make it clear that “COVID has been transmitted by air” and advise accordingly.
Jimenez, Mackay and Milton do not report any relevant financial relationship.
Judy Stone, MD, is an infectious disease specialist and author of Resilience: One Family’s Story of Hope and Triumph Over Evil and Conducting Clinical Research, the essential guide to the topic. You can find her on drjudystone.com or on Twitter @drjudystone.
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