Some diseases are serious that many animals and people get sick and die. For example, bacteria (plural of bacterium) can make people sick with diarrhea, while viruses cause Mad Cow Disease and AIDS.
The bacterium and the virus are the same in many ways, but they have some big differences. The smallest bacterium is bigger than the biggest virus (ASM, 1999). The bacteria can stay alive even if it is outside the animal, but the virus cannot. Some bacteria are useful and helpful, for example lactobacilli bacteria that help people digest food, but all viruses are not helpful at all. Which of these two germs makes us sick with influenza or flu The virus. The influenza virus causes the sickness called influenza or flu.
Animals and humans can get sick with the flu. We know what happens when we have the flu: we get a fever, our body is in pain, and we cannot go to school or to work because we feel weak. Animals cannot tell us how they feel, but scientists know that animals sick with the flu feel weak because they do not move, staying in one place until they get well or die.
There is another difference between the bacteria and the virus. When the virus is inside the animal, it can change itself and become another virus, something the bacterium does not do. This change is called mutation. When a virus changes or mutates, it becomes another virus, so the medicine used to cure the first virus cannot be used to cure the new virus. This is what makes viruses (plural of virus) dangerous.
What is bird flu and how does it spread
Bird flu, also known as avian flu, is the sickness caused by the flu virus in birds. There are many types of flu viruses, and scientists know that a virus called H5N2 is what causes bird flu.
Bird flu spreads quickly in some types of birds like chickens because chickens live very close together, for example in a poultry farm. We see the same with people. If someone in the house gets sick with the flu, I also get sick, and others in the house get sick too. The flu virus spreads from one sick animal or person to another who is healthy. Then, the healthy animal or person becomes sick.
When the virus gets inside the body of a living animal, it starts multiplying. Scientists discovered many years ago that a virus is just a few pieces of DNA, just like what all living animals have inside each cell in the body. Once the virus is inside a living animal, it goes to the cell and starts to live and tell the cell to bring out new cells. But the new cells are like the virus and not like the cells in the body, so the body gets sick because our immune system knows there is something (the new cells that are like the virus) that should not be there. This is called infection, so the body starts fighting infection and that is how we get sick.
This is like when I enter a classroom where I should be studying English, but I make a mistake and enter a classroom where they are teaching French. You know something is wrong because when you talk to your classmates in English, they answer in French. They will tell you to get out of there. This is what the body says to the virus: get out!
There are many ways to spread the virus to other people. When someone sick sneezes or coughs without covering his mouth and nose, the cold and flu viruses stay in the air and can enter your lungs. Some viruses land on the doorknob or the light switch, so when you touch it, the viruses go