Eli5-If a virus isn’t technically alive, I would assume it doesn’t have instinct. Where does it get its instructions/drive to know to infect host cells and multiply?
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A virus is a non-living piece of biological material. It cannot eat, it cannot move, it cannot do anything on its own. It has no drive, motives, instincts, or thoughts.
A virus gets it’s genetic material into a cell, and the cell uses that to make all the pieces to make new viruses, which it does until something else stops it (the cell dying, for instance).
An analogy might be if you stood next to a jet airplane with the turbine running, then picked up a piece of scrap metal and tossed it into the the engine. All sorts of pieces of metal shoot out of the jet engine as the original piece tears through it. Each one of those is capable of being tossed into another jet engine and producing lots of other bits of metal. The metal scrap does this by using up the engine’s own fuel, energy, and materials to produce to pieces of scrap; all it needed was the occasion to happen into the intake of the engine — and that’s all the new pieces need.
Exactly how the virus gets its genetic material into the cell varies, but it’s typically a matter of some part of the virus having a specific shape on it’s surface whereby it gets caught on the cell surface and tugged into the cell, which breaks it apart as it would other things that get in. The genetic material might be DNA that is drawn into the nucleus, or RNA that the cell acts on immediately. In any event, the cell blindly processes the genetic material if it were native and makes virus parts.
Cells make lots of viruses, and while the genetic machinery is really good, it’s not perfect. Mistakes are made, and the viruses change over time. If the bits that help it get into a cell change too much, the virus can’t infect and those ones never go anywhere. If, however, it makes it more effective, the virus spreads faster. The closes thing the virus has to “drive” is that natural selection is only going to let the viruses that infect well continue to infect, and the better, the wider the spread.
The organism and the environment do the movement for the virus, which might float through the air or water, or be passed around in bodily fluids. Maybe the blood will carry the viruses around a body, or lungs slosh them about and fire them through the air with a sneeze or cough.
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