Viruses can't indicate as animal or plant, but this creature are alive and break of infected organ. Viruses are very small, the size may similar with our DNA so viruses can joint to our DNA system become different structure and if the new structure have different fast with other cell then this new system will grow faster than other and become a tumor on our body.
Viruses size about 1/1000 time of bacteria size, so viruses also can infect of bacteria, and causes the bacteria died. Actually viruses are very weak, but on suitable condition viruses can grow very fast. The speed of viruses growing can be similar with Einstein formula like E = mc2. This speed like speed of light.
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