Dear Gianni,

Our planet is home to more than seven million amazing animal species. While we have our differences, we also have something in common: We are all made up of a bunch of cells.My friend Jeb Owen told me all about it.

He’s a scientist at Washington State University who is really curious about how insects eat blood and interact with animal hosts. He’s even been called a disease detective, tracking down viruses transmitted by insects.

We can think of animal cells as water balloons, Owen said. Of course, cells hold more than just water. Inside cells are different parts—almost like a little working kitchen—making things our bodies and cells need.

The cell also holds the animal’s genetic material, or DNA, that acts like a little cookbook. The cookbook is the genetic material that has all the instructions for what makes you, well, you. The outsides of cells have small openings to move things in and out of the cell.

But viruses don’t have all the parts cells have. In fact, a virus is really just a bit of genetic material wearing a protective coat. It’s like a little cookbook without a kitchen. So, viruses can’t make anything on their own. A virus needs a cell to make more viruses using the cell’s kitchen. In a way, viruses are a bit like burglars. They’ve got special “keys” on their coats they use to get through the openings on the outsides of cells.

Once a virus breaks in, it can trick the cell into making more of the virus. The cell makes so much virus the cell bursts like an over lled water balloon, releasing all the new virus copies. When the cells burst, it can make it hard for the body to work, which causes sickness. The immune system, which defends the animal’s body against infection, may recognize something unusual is up.

Sometimes if enough virus gets in, the immune system that works to protect you also ends up causing harm. Cells that protect you and kill off the virus end up killing healthy cells in the process. This can also make us sick.

Some viruses put their genetic material into the genetic material of the animal’s cells. This can make animal cells misbehave and become cancerous. Cancer cells cause your tissues, or the community of cells working together, to fail. This can make you very sick, too.

Most viruses only infect one kind of animal. Even though animals are related, there are small differences in the cells of each kind of animal. It is like the cells of different animals have specific doors and locks on the outsides of the cells. Viruses open those “locks” and can only use that kind of animal as a host. When viruses develop “keys” that work on more than one kind of cell, they can move between different kinds of animals.

It’s a great question you ask, Gianni. Scientists are curious about it, too. After all, knowing more about viruses can help us understand how they move around and how to prevent them. In that way, we can help our animal—and people—friends live even better lives.


Dr. Universe

Jeb Owen also leads an elementary school program in Pullman that brings together art and science. Send us your drawings or write your own story about animals, cells, or viruses:



  • Ask Dr. Universe connects K-8 students with researchers at Washington State University through Q&A. Students can submit science questions on the ASK page.
  • Are you a teacher, parent, or curious grown-up? Follow along on Twitter or Facebook.
  • Do you want to reprint this Q&A? Just send a message to