Getting Technical
MIT News
Figure 1 also shows clearly how much smaller viruses generally
are than bacteria which explains to some extent the different
opinions on the effectiveness or otherwise of people getting
infected when wearing face masks by breathing in the Corona
Covid-19 or spreading the virus when exhaling. A further
complication in assessing how effective face masks are is
whether Covid-19 coming into contact with masks are just the
viruses as such or the viruses contained in much larger droplets
of fluid or saliva sprayed out by sneezing and coughing.
In recent years nothing has grabbed the attention of the populace
world-wide as much as the escalating mortality toll caused by the
onslaught of this virus as it continued to spread.
Different types of viruses can infect only a limited range of hosts
and many are species-specific. Some, such as the smallpox virus for
example, can infect only one species—in this case humans.
Other viruses, such as rabies virus, can infect different species of
mammals. The viruses that infect plants are harmless to animals
and most viruses that infect animals are harmless to humans.
The host range of some particular viruses is limited to a
single strain of bacteria which enables these viruses to be used to
trace the source of outbreaks of certain infections.
Viruses are the only type of microorganism that cannot
reproduce without a host cell. Before entering a cell,
viruses exist in a form consisting of two or three distinct parts:-
genetic DNA or RNA; a protective coat of protein; a lipid (a type
of fatty liquid) envelope around the protein coat when the virus is
by itself and not inside a cell. After contacting a host cell, a virus
inserts genetic material into the host and continues to reproduce.
It is this process that classifies viruses as parasites. The three main
shapes of viruses are:
• Helical: An example is the tobacco mosaic virus
• Icosahedral (approximately spherical): Most animal viruses
are this shape
• Envelope: Having a protective lipid envelope as mentioned
above. An example is HIV.
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RACA Journal I August 2020
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