- Can't replicate without a host, but can live on surfaces
- Many virus infections don’t cause symptoms at all. In some cases, viruses can cause significant disease, especially in certain groups of people (such as young kids, elderly adults, pregnant women).
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- Can live on its own.
- Normally occurring bacteria help digest food, can destroy disease-causing microbes, fight cancer cells and provide nutrients. However, bacteria can occasionally cause serious infections.
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