Transmission modes
How do asymptomatic carriers
make
the SARS-CoV-2 virus transmission and infect others?Because they do not
cough or sneeze to any appreciable extent by definition, the direct or
indirect contact modes and aerosol transmission are considered as the
main possible modes of transmission[36]. Public health messages
have paid attention to
the
possibility of direct and indirect transmission such as by contaminated
hands, stressing the importance of washing hands often and thoroughly.
Now we need to focuse on aerosol transmission. During the SARS
epidemic in 2003, it has been verified that these infected hospitalized
patients emitted viable aerosolized virus into the air[37]. A recent
resarch by Doremalen et al. demonstrated that “aerosol and fomite
transmission of SARS-CoV-2 is plausible, since the virus can remain
viable and infectious in aerosols for hours and on surfaces up to
days”[38]. It had been confirmed long before that ordinary
breathing and speech both emit large quantities of aerosol
particles[39, 40]. So the asymptomatic or pre-infected individuals
still generate aerosols even if they do not sneeze or cough. Other
studies have found that vocalization can emits up to
an order of magnitude more aerosol
particles than breathing, and the louder one speaks, the more aerosol
particles are produced[41, 42].
It has been concluded by some researchers that COVID-19 can be
transmitted by a face-to-face conversation with an asymptomatic
infection individual without no touch, which ascribed to a large number
of exhaled particles released during breathing and speech and the high
transmissibility of SARS-CoV-2[36]. But how do the virus titers in
these aerosols change with time after infection or discharge, and what
is the best way to avoid infection from the point of environmental
aerodynamics? Scientists need collaborate and take up the current
challenge presented by COVID-19. At the same time, more publicity is
needed to inform the public that
everyone
releases potentially infectious aerosols all the time, not just when
sneezing or coughing, so it is essential to avoiding close contact and
wearing a mask with protective properties.