Dr. Universe: How do germs enter the body? -Amari, 8, Indiana
 
Dear Amari, 
 
There are many different ways germs can enter the body. Sometimes they find a way in through an opening like the mouth, nose, eyes or a cut in the skin.   
 
Most of these germs—what scientists call viruses and bacteria—are so small we’d need a microscope to see them. 
 
My friend Leigh Knodler is a researcher at Washington State University who works with a particular kind of bacteria called Salmonella.  
 
Salmonella can sometimes live on food, such as undercooked chicken or unwashed fruits and vegetables. It typically enters the body through the mouth when someone takes a bite of food.  
 
If we followed Salmonella through the body, it would pass through the esophagus, the stomach and finally into the intestines.  
 
It turns out that lots of germs have to cross a kind of membrane, or barrier, to get into the body’s system. For instance, Salmonella must cross a membrane that lines the intestines.  
 
When the bacteria pass through the membrane, they can get into the blood and circulate through the body.   
 
Sometimes germs will also pass through the thin membranes that cover the eyeballs when we touch our eyes and face. It’s rare, but even Salmonella can sometimes enter the body this way.  
 
Finally, some germs can enter through the nose as well. When germs in the air make it down into someone’s respiratory system, the germs can pass through the membranes of the lungs and into the blood. For instance, SARS-CoV-2, the virus that causes the novel coronavirus, often enters the body through the nose or mouth through tiny saliva droplets. The virus travels down into the airways and into the lungs.  
 
While some germs might enter the body through contaminated food or saliva, other germs might find a way into the body through the bites of mosquitos or ticks. The viruses and bacteria do what they can to survive and reproduce.  
 
But the good news is you have a system that is primed and ready to defend you when they arrive. The immune system, which is made up of different cells, tissues and organs, can recognize that the invaders might make you sick. The system kicks into gear and works to help protect you.  
 
You know, not all bacteria are bad, but there are things we can do to help keep the bad germs from spreading around. For instance, we can cover our mouths when we cough or sneeze. With the novel coronavirus, we can wear facemasks that help us keep our germs to ourselves and help stop SARS-COV-2 from spreading to others. We can also wash our hands frequently, especially before we eat, drink, prepare food or use the restroom.  
 
It’s also great to know that there are scientists who study viruses and bacteria, including Salmonella, to help us better understand these germs and how they work.  
 
Through research, people are developing vaccines and medications that can help us prevent the spread of viruses and bacteria— and help improve the health of humans all around the world.  
 
Sincerely,
Dr. Universe