HEAD OF CHEMISTRY DEPARTMENT
14/29-A Samanabad Lahore Pakistan ID No 35202-8963627-3 Cell No 03336700587
So far, scientists consider two ways of coronavirus transmission. One is
infection coming from contact with some object, that has virus on it. The other
one is by inhaling droplet emitted by sneezes and coughs of infected person. But
some experts say that there is third infection route also. That is through
micro-droplets that makes the spread somewhat akin to aerosol/airborne. It is
alarming and demands some extra methods of protection.
There are new facts about infection mechanism of Coronavirus shown in NHK
Documentary. Experts are looking at this new infection mechanism as the crucial
step to prevent the further spread of the virus.
Kazuhiro Tateda, President The Japanese Association for Infectious Disease,
says: “It seems transmission are happening during conversations and even when
people are standing at a certain distance apart. These cases cannot be explained
by ordinary droplet infection. We think infection comes from "micrometer
particles". This transmission can be called "micro-droplet infection".
So how does, it takes place. In each case is conducting an experiment with the
group of researchers. The team tracks particles in the air by using laser beam
and then observing them by the high sensitivity camera. This technology allows
to detect droplet as small as 0.1 micrometer (1/10,000 mm) wide. The experiment
started, when a person was irritated to sneeze by rubbing inside nasal cavity
with a straw. He sneezed, they saw large droplet of about 1mm diameter, that
quickly fell on earth. Then looked through high sensitivity camera. They saw the
small particles that seem to floating to the air. These particles are smaller
than 10 micro meter or 1/100 of mm in diameter.
Then, they saw sneezing droplet from a different angle, the droplets were small
and light and were drifting in the air. These are micro-droplets.
They came to know that sneezing was not the only source of these droplets. They
ran the same experiment on a close range conversation, people generated a lot of
micro-droplets when they talk loudly, the droplet between the two talking
persons stayed where they were. They didn't drift away.
It is not yet known; what volume of micro-droplet leads to infection. But Tateda
says; “We can’t rule out the possibility that micro-droplets have spread the
virus to some extent”.
Tateda says: “Micro-droplet carry many viruses. We produce them, when we talk
loudly or breathe heavily. People around us inhale them and that's how virus
spread. We are beginning to see this risk now".
The risk of infection through micro-droplet becomes even greater in close space
with poor ventilation.
The lab simulated the move of micro droplet in an air tight room, equal to the
size of a classroom, the 10 people were in enclosed it. A person coughed once
and spread about one hundred thousand droplets. Large droplet in simulation were
shown in blue and green; most of these fell to the ground within 1 minute. But
the micro-droplets shown in red continue to drift. In another simulation, which
only showed micro-droplet, 5 minute later, 10 minute later, 20 minute later; the
micro-droplets were still floating in space.
Masashi Yamakawak, Associate Professor, Kyoto Institute of Technology said: "If
the air is not flowing, the micro-droplet won't move. And since they can't move
on their own, they stay in place for some time”.
“But there is a way to prevent this stagnation of micro-droplets; by opening
windows and increasing air circulation, it is believed to be effective. When you
open a window, micro-droplets are quickly swept away. They are very small and
light, so any air flow will get rid of them.” While Fateda says: “What's
important is to create two openings. Do this at least once an hour. That lower
the risk of infection considerably.”
Chines conducted a research on Aerodynamic Characteristics and RNA Concentration
of SARS-CoV-2 Aerosol in Wuhan Hospitals during recent COVID-19 Outbreak, as the
transmission of COVID virus through human respiratory droplets and by contact
with infected persons was clear, the aerosol transmission had been little
The researchers took 35 aerosol samples of three different types; total
suspended particle, size segregated and deposition aerosol) and were collected
from Patient Areas and Medical Staff Areas of Renmin Hospital of Wuhan
University (Renmin) and Wuchang Fangcang Field Hospital (Fangcang), and Public
Areas in Wuhan, China. A robust droplet digital polymerase chain reaction (ddPCR)
method was employed to quantitate the viral SARS-CoV-2 RNA genome and determine
aerosol RNA concentration.
Results showed that the ICU and general patient rooms inside Renmin, patient
hall inside Fangcang had low airborne COVID virus concentration but deposition
samples inside ICU and air sample in Fangcang patient toilet tested positive.
The airborne COVID virus in Fangcang Medical Staff Area had bimodal distribution
with higher concentration than those in Renmin during the outbreak but turned
negative after patient’s number reduced and rigorous sanitization implemented.
Public Area had undetectable airborne COVID virus concentration but obviously
increased with accumulation of crowd flow.
Researchers concluded that room ventilation, open space, proper use and
disinfection of toilet can effectively limit aerosol transmission of COVID
virus. Gathering of crowds with asymptomatic carriers is a potential source of
airborne COVID virus. The virus aerosol deposition on protective apparel or
floor surface and their subsequent resuspension is a potential transmission
pathway and effective sanitization is critical in minimizing aerosol
transmission of COVID virus.
Apart from this study, Chines have said: the droplets remain in air for 3 hours
and some Chines scientists have suspected that 60% of infection spread through
Researchers examined air and surface sample of three COVID patient A, B and C in
Singapore. 26 samples were taken from patient room, ante room, and the bathroom.
The sample of patient A and B were taken after cleaning, and found all were
negative. For patient C, whose samples were collected before cleaning, they
found positive result with 13(87%) of 15 room sites and 3 (60%) of 5 total sites
testing positive result for virus. All air sample were negative.
These were all special isolation rooms with special kind of ventilation. The
fact that air exhaust outlet tested positive suggests that small virus droplet
was displaced and landed there.
But it is important to remember that all of these studies looked at viral RNA
and viral particle. But we don’t know whether these viral particles were still
viable and able to infect human. So how long will viral particle survive? After
they fall on the surface or get suspended in the air, will they stay viable to
Researcher looked at this also. They suspended the virus in air and on various
surfaces like copper, cardboard, stainless steel and plastic, and took samples
at various time points; they then look to see whether that virus was still able
to infect cases. They found SARS COV-2 was most stable on plastic up to 72 hours
(3 days); followed by stainless steel with 48 hours (2 days); cardboard 24 hours
(1 day) and copper 8 hours.
Areoles virus remain viable for the entire experiment when lasted three hours.
In the last statement of the paper, researchers say: if there is ongoing
contradictory finding in multiple studies (as with the influenza virus), and
Sars-Cov-2, it may be more likely that the various transmission routes may
predominate in different settings, making the airborne route for that particular
pathogen more of an opportunistic pathway, rather than the norm.
This mean that the airborne route is probably mainly relevant for certain
situations and that would be the hospital, hospital staff room, hospital
changing room as well as crowded and badly ventilated public spaces.
Everyone else is probably more likely to get the virus through touching surfaces
and bad hand hygiene and then touching their face.
In summary, data suggest that concentration of suspended virus in the air
increases form almost no virus in public places, ICU and isolation rooms. To a
little more in crowded outdoors, even more in medical staff rooms, and patient
toilets. A lot more in staff change rooms, where they take off their protective
In general, the concentration of virus in the air inside hospital seems to be
low but may be significantly elevated when staff has spent long hours with
patient so droplet/aerosol deposited on their protective gears. When they then
take off protective equipment, the positive material might become re-suspended
in the air.
Medical staff might have false sense of security when they are outside the
patient rooms like in medical staff rooms or changing room. But the data suggest
that these are places where most likely to be infected.
What the data also show is that patient toilet seem to be particularly prone to
contamination and high clean measures seem to be necessary to prevent
The researchers of Aalto University, the Finnish Meteorological Institute, the
state-owned technical and innovation centre VTT and Helsinki University
conducted a research on COVID transmission route and found that coronavirus
droplets ejected when a person coughs, sneezes or even speaks can remain
suspended in the air for minutes rather than immediately sinking to ground. The
droplet are extremely small aerosol particles and travel on air currents.
Differentiation between aerosol/airborne and droplet transmission:
Dr. Wong Sin Yew, infections disease specialist, differentiated aerosol/airborne
transmission and droplet transmission in these words:
“In aerosol transmission, equivalent to term airborne transmission, usually the
particle size is less than 10 micro meter. When you talk about droplet; particle
size tends to be larger than 20 micro meters usually. If you have larger size,
droplet travel lesser distance. Where for aerosol/airborne transmission,
distance can be much farther. In airborne, just the breathing out, can transmit
the virus. So aerosol/airborne can affect both near and long distance people.
Whereas the droplet transmission is only 1 to 2-meter range.
Furthermore, aerosol/airborne is spread by coughing, sneezing, talking and
exhaling. Whereas droplet transmission is confined to coughing and sneezing
only”. People who inhale the airborne germs do not have to have face-to-face
contact or be in the same room as the infected person. It can go across the
room. Aerosol goes to person’s lung while droplet mostly reach trachea.
If a common science students look on above findings of Japanese Chines and
Singaporean; one can guess that when droplets outburst, there are chances of
range of various sizes; micro, medium and macro. Then there is also chance that
some of medium size droplets to evaporate and become smaller, often called
So, keeping in mind, Japanese finding, Chinese studies, Singapore research,
Finland report and Dr. Wong Sin Yew’s differentiation. It seems that COVID’s
virus droplet of 10 micro meter can have some small sort of aerosol/airborne
transmission. However, mostly it is droplet transmission.
Whether the finding of Japanese, Chinese, Singaporean, Finnish are accurate or
not? Sagacity demands to give them due consideration for the time being, till
the exact mode of spread is confirmed and it is of prime importance to adopt
precautionary measurement for all three modes of transmissions.