How your body fights off viruses

You wanted to know

"How do viruses attack the body and make you sick?" asked a sixth-grader in Gregg Thompson's social studies class at Woodland Middle School in Gurnee.

A virus is an organism that enters cells and replicates and, in doing so, injures or destroys cells. Viruses are found everywhere in the world where cells exist.

Attending Physician Larry K. Kociolek, division of infectious diseases and associate medical director of infection prevention and control at Ann & Robert H. Lurie Children's Hospital of Chicago, said there are plenty of ways viruses enter a body and there are many ways to protect against these unwelcome organisms.

"You can breathe some viruses into your nose, throat and lungs if someone nearby coughs or sneezes viruses into the air. That is why it is a good idea to always cover your coughs and sneezes to prevent other people around you from getting sick," Kociolek said.

"Some viruses are passed from person to person after shaking hands or sharing objects with someone who is sick. If these viruses are on your hands, they can enter the body if you rub your eyes, or the viruses can be swallowed when you eat or drink. That is why it is a good idea to always wash your hands before meals, after coughing or sneezing in to your hands and after you use the restroom."

A virus can only do one thing - replicate. It can be a danger to some species but not others, such as viruses that affect plants but not people. Knowing they are expert at replicating, scientists have figured out how to use viruses to treat illness - for example, the adenovirus is used experimentally for gene therapy which can help kill cancer.

Sometimes the immune system is unprepared to fight a virus, Kociolek said.

"Different viruses like to attack different parts of the body," he explained. "Some viruses, like the flu, attack the cells in the nose, throat, airways and lungs. Other viruses may attack the cells in the intestines, brain cells, heart muscle cells or cells that control our immune system. When the cells are injured, you feel sick."

In most cases, the immune system wins the battle.

"Most of the time, your immune system will remember the virus that made you sick," Kociolek said. "If the same virus enters your body again in the future, the immune system will kill the virus before you get sick. This is why it is a good idea to get vaccines. Vaccines stimulate the immune system to kill viruses before they make you sick."

Antibiotics cannot kill a virus.

The best weapon against this invader is your immune system, on its own or with the help of vaccines. Vaccines use a weakened or killed version of the virus, or antigens, so your cells can build resistance in the form of antibodies.

Most children are vaccinated for several viruses, including measles, mumps, rubella, polio, Hepatitis A and B and chickenpox. Once vaccinated, if the virus tries to enter cells, antibodies respond that recognize and destroy it.

Smallpox is an example of a virus that once killed more than 30 percent of people it infected - more than 300 million in the 1900s. For the past 40 years, the world has been smallpox-free, and in the U.S. the vaccine is no longer provided because vaccines eliminated the disease.

One way to fight the adverse microorganisms is to become a physician. Kociolek's work includes health care epidemiology, or the study of disease control, and studying ways to prevent healthcare-related infections.

Another career that involves the study of viruses is microbiology. The work day of a microbiologist can involve more than looking at slides under a microscope, according to the American Society for Microbiology.

According to microbeworld.org, the society's website, "Microbiologists work in the food industry, water treatment, agriculture, pollution control, biotechnology, energy development, museum preservation and many other disciplines. Microbiologists can be found in a variety of settings, from the traditional laboratory to the woods."

Check it out

The Warren-Newport Public Library District in Gurnee suggests these titles on viruses:

• "Micro Mania" by Jordan D. Brown

• "Danger! Open with Extreme Caution! Viruses" by Natalie Goldstein

• "Bill Nye the Science Guy's Great Big Book of Tiny Germs" by Bill Nye

• "Viruses Up Close" by John Shea