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Unit 19: Biology Part 2 Page 81 of 137
A third group of pathogens are described because they are not
protozoa. Protozoa have a single alive. Viruses inject DNA, the
cell, like bacteria, but they have a genetic material into cells. This
nucleus. allows the viruses to take over the
cells and multiply. Viruses are
One serious disease caused by responsible for many common
protozoa is malaria. More than a infectious diseases, including colds
million people die from this and the flu.
infectious disease each year.
Mosquitoes transfer the protozoan
that causes malaria from one
person to another when they bite
them.
Some protozoa also cause
diarrhea. Although diarrhea may
just seem like an inconvenience to
us, in some poor countries people
die of the dehydration caused by
diarrhea.
Figure 69 – Viruses like H1N1,
the virus responsible for
“swine” flu, inject DNA into
cells to take them over.
Unfortunately, viruses do not
respond to antibiotics. Medicines
called antiviral drugs can treat
diseases caused by viruses, but
often times the best thing for a
person with a cold or the flu to do
is drink plenty of fluids and get lots
Figure 68 – The protozoan of rest.
Giardia lamblia causes
intestinal diseases, which may How Are Pathogens
lead to diarrhea.
Spread?
A final group of pathogens are
viruses. Viruses are different than Different pathogens are spread in
the other pathogens we have different ways. Giardia lamblia,
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