Posts
Coronavirus
can travel twice
as far as official ‘safe
distance’ and stay in
air for
30 minutes, Chinese study
finds
-
Authorities advise people to stay 1-2 metres apart, but researchers found that a bus passenger infected fellow travellers sitting 4.5 metres away
-
The scientists behind the research said their investigation also highlighted the importance of wearing face masks because of the length of time it can linger
SCMP,
9
March, 2020
The
coronavirus that causes Covid-19 can linger in the air for at least
30 minutes and travel up to 4.5 metres – further than the “safe
distance” advised by health authorities around the world, according
to a study by a team of Chinese government epidemiologists.
The
researchers also found that it can last for days on a surface where
respiratory droplets land, raising the risk of transmission if
unsuspecting people touch it and then rub their face.
The
length of time it lasts on the surface depends on factors such as
temperature and the type of surface, for example at around 37C (98F),
it can survive for two to three days on glass, fabric, metal, plastic
or paper.
These
findings, from a group of official researchers from Hunan province
investigating a cluster case, challenge the advice from health
authorities around the world that people should remain apart at a
“safe distance” of one to two metres (three to six and a half
feet).
Their
work was based on a local outbreak case on January 22 during the peak
Lunar New Year travel season. A passenger, known as “A”, boarded
a fully booked long-distance coach and settled down on the second row
from the back.
The
passenger already felt sick at that point but it was before China had
declared the coronavirus outbreak a national crisis, so “A” did
not wear a mask, nor did most of the other passengers or the driver
on the 48-seat bus.
“It
can be confirmed that in a closed environment with air-conditioning,
the transmission distance of the new coronavirus will exceed the
commonly recognised safe distance,” the researchers wrote in a
paper published in peer-review journal Practical Preventive Medicine
last Friday.
The
paper also highlighted the risk that the virus could remain afloat
even after the carrier had left the bus.
The
scientists warned that the coronavirus could survive more than five
days in human faeces or bodily fluids.
They
said the study proves the importance of washing hands and wearing
face masks in public places because the virus can linger in the air
attached to fine droplet particles.
Hu
Shixiong, the lead author of the study who works for the Hunan
Provincial Centre for Diseases Control and Prevention, said the
security camera footage showed patient “A” did not interact with
others throughout the four-hour ride.
But
by the time the bus stopped at the next city, the virus had already
jumped from the carrier to seven other passengers.
These
included not only people sitting relatively close to “patient
zero”, but also a couple of victims six rows from him – roughly
4.5 metres away.
They
all later tested positive, including one passenger who displayed no
symptoms of the disease.
After
these passengers left, another group got on the bus about 30 minutes
later. One passenger sitting in the front row on the other side of
the aisle also became infected.
The
coronavirus that causes Covid-19 can linger in the air for at least
30 minutes and travel up to 4.5 metres – further than the “safe
distance” advised by health authorities around the world, according
to a study by a team of Chinese government epidemiologists.
The
researchers also found that it can last for days on a surface where
respiratory droplets land, raising the risk of transmission if
unsuspecting people touch it and then rub their face.
The
length of time it lasts on the surface depends on factors such as
temperature and the type of surface, for example at around 37C (98F),
it can survive for two to three days on glass, fabric, metal, plastic
or paper.
These
findings, from a group of official researchers from Hunan province
investigating a cluster case, challenge the advice from health
authorities around the world that people should remain apart at a
“safe distance” of one to two metres (three to six and a half
feet).
Their
work was based on a local outbreak case on January 22 during the peak
Lunar New Year travel season. A passenger, known as “A”, boarded
a fully booked long-distance coach and settled down on the second row
from the back.
The
passenger already felt sick at that point but it was before China had
declared the coronavirus outbreak a national crisis, so “A” did
not wear a mask, nor did most of the other passengers or the driver
on the 48-seat bus.
“It
can be confirmed that in a closed environment with air-conditioning,
the transmission distance of the new coronavirus will exceed the
commonly recognised safe distance,” the researchers wrote in a
paper published in peer-review journal Practical Preventive Medicine
last Friday.
The
paper also highlighted the risk that the virus could remain afloat
even after the carrier had left the bus.
The
scientists warned that the coronavirus could survive more than five
days in human faeces or bodily fluids.
They
said the study proves the importance of washing hands and wearing
face masks in public places because the virus can linger in the air
attached to fine droplet particles.
“Our
advice is to wear a face mask all the way [through the bus ride],”
they added.
Hu
Shixiong, the lead author of the study who works for the Hunan
Provincial Centre for Diseases Control and Prevention, said the
security camera footage showed patient “A” did not interact with
others throughout the four-hour ride.
But
by the time the bus stopped at the next city, the virus had already
jumped from the carrier to seven other passengers.
These
included not only people sitting relatively close to “patient
zero”, but also a couple of victims six rows from him – roughly
4.5 metres away.
They
all later tested positive, including one passenger who displayed no
symptoms of the disease.
After
these passengers left, another group got on the bus about 30 minutes
later. One passenger sitting in the front row on the other side of
the aisle also became infected.
Hu
said the patient, who was not wearing a mask, was likely to have
inhaled aerosols, or tiny particles, breathed out by the infected
passengers from the previous group.
Aerosols
are light-weighted particles that are formed from tiny droplets of
bodily fluids.
“The
possible reason is that in a completely enclosed space, the airflow
is mainly driven by the hot air generated by the air conditioning.
The rise of the hot air can transport the virus-laden droplets to a
greater distance,” said the paper.
After
getting off the shuttle bus, the initial carrier got on a minibus and
travelled for another hour. The virus jumped to two other passengers,
one of whom was also sitting 4.5 metres away from patient “A”.
By
the time the study was finished in mid February, patient “A” had
infected at least 13 people.
It
is generally believed that the airborne transmission of Covid-19 is
limited because the tiny droplets produced by patients will quickly
sink to the ground.
his
belief has prompted the Chinese health authorities to suggest that
people should stay a metre apart in public and the US Centres for
Disease Control recommend a safe distance of six feet (about 1.8
metres).
The
researchers also found that none of those passengers in the two buses
who wore face masks were infected.
They
said it vindicated the decision to ask people to wear a face mask in
public.
“When
riding on more closed public transportation such as subways, cars,
planes, etc, you should wear a mask all the time, and at the same
time, minimise the contact between your hands and public areas, and
avoid touching your face before cleaning,” they said.
The
researchers also suggested improving sanitation on public transport
and adjusting the air conditioning to maximise the volume of fresh
air supplied.
They
also said interiors should cleaned and disinfected once or twice a
day, especially after passengers arrive at the terminal.
A
doctor in Beijing involved in the diagnosis and treatment of Covid-19
patients said the study had left some questions unanswered.
For
instance, the passengers sitting immediately next to the carriers
were not infected, though they were suffering the highest exposure to
the disease-bearing aerosols.
“Our
knowledge about this virus’s transmission is still limited,” he
said.
Compare
that with this (behind a paywall)
(Bloomberg)
— Forget face masks and rubber gloves. The best way to avoid the
coronavirus is frequent hand washing, according to a medical adviser
to the world’s airlines.
The
virus can’t survive long on seats or armrests, so physical contact
with another person carries the greatest risk of infection on a
flight, said David Powell, a physician and medical adviser to the
International Air Transport Association. Masks and gloves do a better
job of spreading bugs than stopping them, he said.
As
concern mounts about the scale of the outbreak, carriers from United
Airlines Holdings Inc. to Cathay Pacific Airways Ltd. have scrapped
thousands of flights to China. Here is an edited transcript from an
interview with Powell. IATA represents about 290 airlines and more
than 80% of global air traffic.
No comments:
Post a Comment
Note: only a member of this blog may post a comment.