Warts are caused by viruses. Viruses have just a few genes (we all have genes – these are the instructions for making all of our parts). Unlike you and me and animals and plants and even other types of germs, all of which have thousands of genes, viruses have just a few; really just enough to make a little box so the virus can spread from one cell to another and even from one person to another.

The virus that causes warts infects human skin cells. The virus causes the skin cells to divide into more cells and this produces a little bump of cells. The virus is called the human papilloma virus and the little bumps are called papillomas by doctors. The rest of us call them warts! Sometimes the wart can be in a place where it gets hit and they hurt and bleed a little. We tend to get warts as children and very often they go away as we get older.

The virus is spread from another person when dead cells with virus inside them fall off the wart and land on someone else. The wart virus is very common, so it's easy to get warts when you're a kid. Viruses can be very fussy! The virus that causes warts only infects skin cells. In fact, human papilloma viruses are so fussy about the cells they will infect that they only cause warts on humans. Many animals have their own wart viruses! So, your dog or even a cow may have warts but you can't give warts to them and they can't share their warts with you.

It's amazing how much viruses bother us when you realize that they are for the most part just little boxes (or virus particles) containing so few genes. When they are not inside our bodies, they can't make more virus particles. But they are awesome parasites (a small organism living on another organism) because once a virus particle gets into a cell it can take over the cell's machinery and direct the cell to make lots of new viruses. Some viruses can direct the cell to make hundreds or even thousands of new virus particles.

While viruses are very fussy about which cells they will infect, there are many different viruses and so, almost any cell can be infected by some virus. The papilloma viruses prefer skin cells, but the influenza virus infects the cells of the respiratory tract, rotaviruses infect our gastrointestinal tract and poliovirus can infect the nerves. The rotaviruses are remarkable. They multiply very quickly and can make you "sick to your stomach" within 18 hours of getting into your small intestine!

Luckily for most of us our bodies develop a very strong immune response (or defense) to viruses and can rapidly stop them from invading our cells and multiplying. In fact, very often by the time you have symptoms, the immune response already has the virus on the run and sometimes the symptoms are actually due to the immune response itself. The body is somewhat slow in responding to the wart viruses and that's why warts sometimes last for a couple of years or more before they go away.

The other great thing about the immune response is that it often will protect you for life from getting infected with the same virus again. That's why we tend to get warts as children but don't get them again as adults. The problem is that there are so many different viruses! Over 100 viruses cause the common cold, so we get colds over and over again, usually two to three times each year. But only one virus, the measles virus, causes measles so most people get measles just once in their lives. Today's children and many of their parents will never get measles because we have a very good vaccine or shot which prevents infection by the measles virus. We also have good vaccines for the mumps and polio viruses, so very few people get these diseases any more. But with so many different viruses causing the common cold, we're probably stuck with the common cold for many years to come.

So, here's the very best advice for avoiding cold viruses-wash your hands, just like your Mom says to! We most commonly spread it by getting it on our hands and then touching our faces. Viruses are so small you can't see them, but if you wash your hands frequently, you can reduce the risk of getting infected.

Thanks for your question,
Aubie and Dr. Roberts