Viruses are even smaller than bacteria and require living hosts — such as people, plants or animals — to multiply. Otherwise, they can't survive. When a virus enters your body, it invades some of your cells and takes over the cell machinery, redirecting it to produce the virus.
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viruses are the smallest and simplest life form known. They are 10 to 100 times smaller than bacteria.; The biggest difference is that viruses most have a living host- like a plant or animal- to multiply, while most bacteria can grow on non-living surfaces.
