Are Viruses Alive?
- Although viruses challenge our concept of what “living” means, they are vital members of the web of life
- The best analogy is that of a seed that under appropriate conditions, it becomes ‘‘alive’’
- A virus differs in that it cannot reproduce unless it is in a host cell
- Think of the virus as the bean and the host cell as the soil
- Viruses cannot multiply on their own, they need cellular components for their replication and protein synthetic apparatus
- Thus, the virus is at the edge of life and can exist in two states—an inert state and a living state
For about 100 years, the scientific community has repeatedly changed its collective mind about what viruses are. First seen as poisons, then as life-forms, then biological chemicals, viruses today are thought of as being in a gray area between living and nonliving: they cannot replicate on their own but can do so in truly living cells and can also affect the behavior of their hosts profoundly.
Do viruses Die?
Strictly speaking, viruses can’t die, for the simple reason that they aren’t alive in the first place. Although they contain genetic instructions in the form of DNA (or the related molecule, RNA), viruses can’t thrive independently. Instead, they must invade a host organism and hijack its genetic instructions.
A virus inside a cell:
- A virus won’t die unless the host immune system detects and destroys the infected cell or the cell dies
- Insert itself directly into the host DNA where it can just sit there, inactive, and never do anything again, until the host dies, or becomes active again in the future events
A virus outside a cell:
- Viruses survive outside our bodies because of how they are built. Specifically, they are pieces of genetic material (RNA or DNA) contained in a special coating of proteins called capsids. Viruses cannot replicate unless absorbed by cells in our body. Once a virus is outside the body, its capsid starts to degrade, and the more degraded its capsid is, the less likely it is to survive. When outside the body, these capsids degrade faster in cold, dry environments. They also degrade faster on soft, rather than on hard surfaces. That’s because they need moisture to survive and soft surfaces absorb that moisture.
- Some viruses may die because their insertion envelope drys up or their machinery may be damaged
- Some – including the influenza virus, and HIV, the virus responsible for AIDS – can’t survive for more than a few hours outside a host organism unless kept under carefully controlled conditions.
- But most viruses can survive very long periods outside a cell and then infect later. For example, the deadly smallpox virus can easily remain infectious for years.
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