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.