VACCINES

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How Viruses Work
Viruses such as the yellow fever virus are
tiny microbes made up of a small number
of genes encased in a membrane or protein
shell. If you were the size of a cell, a virus
would look like a burr (a small, round
object covered with tiny bristles) attached
to your pants leg.
Like burrs, viruses stick to cells. Then they
inject their genetic material inside the cells.
Once inside, the virus genes take over the
cells’ resources and molecular machinery,
forcing the cells to make more viruses.
The newly formed viruses “bud”—or are
released from the surface of the cells and
drift off to infect new cells. Cells infected
with viruses can’t function properly and
usually die. Many are eliminated by killer
T cells.