It's a bit tricky to say that a virus "grows" in the same way a living organism does. Viruses don't have their own metabolism and can't produce energy on their own. Instead, they rely entirely on the host cell to provide the energy and resources for their replication.

Here's how it works:

1. Infection: A virus attaches to a host cell and enters it.

2. Hijacking: Inside the host cell, the virus uses its own genetic material (DNA or RNA) to take over the cell's machinery. It forces the host cell to produce viral proteins and copies of its own genetic material.

3. Assembly: These viral components then assemble into new virus particles.

4. Release: The new viruses are released from the host cell, often destroying it in the process.

The energy used for all these steps comes from the host cell's own energy production, not from the virus itself.

So, while a virus doesn't "grow" in the traditional sense, it does utilize energy from the host cell to replicate and create more virus particles. This is a key aspect of viral infection and its destructive potential.