Viruses are tiny particles that are made up of DNA or RNA, a
protein coating, and sometimes a fatty membrane. They cannot reproduce themselves,
so they use an organism to do it for them. Viruses do this by attaching
themselves to a cell in the organism and inject the virus DNA into the cell. It
is fooled into replicating the DNA and making the protein coatings, which will
combine to form new viruses. The new viruses then exit the cell by exocytosis
or by bursting out of the cell and go on to infect other cells. Viruses can
also mutate into different strains so the immune system doesn’t recognize it.
Before vaccines were invented, many people died of diseases
caused by viruses such as smallpox, mumps, and polio. 1 out of 3 children died before
they were 10 years old because of these diseases. In 1796, Edward Jenner
noticed that some milkmaids did not get smallpox, but they did get cowpox.
Jenner wondered if smallpox and cowpox were related. He then did an experiment
in which he scraped a sore from a milkmaid’s arm and then injected the sore
into an eight year old boy’s arm. Jenner then injected some of the smallpox
virus into the boy. The boy didn’t get infected! Jenner did this with 20 other
people, all of whom did not get smallpox.
Other doctors tried to do the same thing with different
diseases. One doctor injected rabbits with polio, crushed up their spines, and
injected the spines into people to prevent polio. It worked, but over time the
people developed other problems caused by the injection. After this, doctors
stopped using animals to cure diseases.
A large percentage of people need to be vaccinated in order
for the disease to be wiped out. This is why you need to get vaccinated. Washing
your hands and general hygiene can also help to prevent disease.
