Symptoms: What Happens When You Become Infected With 2009 Swine Flu

The virus can enter through your nasal passages or your mouth but this doesn't mean you're automatically infected. The mucous membranes of your nose and throat trap the virus, as well as dust, foreign bodies, and bacteria, rendering them harmless. The small microscopic hairs, called cilia, that line air way passages sweep over 100 times per minute and can sweep the virus right back out. If a virus does get through and enters a body cell it immediately begins the replication process and that's when the trouble starts.

The body cell, once it’s invaded, sends out a distress signal through MHC, a chemical in every body cell, that recognizes what's foreign to the body and what belongs. This chemical boots the viral protein to the surface of the cell. Killer T-cells, a type of white blood cell, sense the distress call and kill the cell and the virus within by coating the cell with toxic chemicals. The dead cells are cleaned up by macrophage cells which surround and consume cellular debris and pathogens.. Histamines increase the blood flow to the area. More blood flow means more killer T-cells.

At this point your throat really, really hurts because the blood vessels swollen with the increased blood are pressing on nerve cells and pain receptors. The body temperature starts to rise as the number of macrophages increase. Your body aches because your pain threshold has been lowered. Fever increases as the body tries to boost new cell production. You get the chills because your muscles contract to generate more heat. Blood flows away from you skin so you feel cold. You get a headache because of the increasing pressure of the swollen blood vessels in your brain. Now, you could take aspirin to bring down the fever but that's counter productive. The fever is one way your body fights against the virus.

If the virus gains momentum and the T-cells start losing the fight the infection spreads to the lungs. The macrophages that have destroyed the dead cells are in the blood stream and pass eventually through a lymph node. The viral material in the macrophage is detected and triggers more production of white blood cells including T-cells. This increased production causes the lymph glands to swell and become tender.

The T-cells go to the site of the viral infection and start destroying more cells which increases the debris. Coughing is how the debris is expelled from the throat and lungs.

The fight isn't over yet. Another immune cell, single B-cells in the lymph glands, produces antibodies that rush to the site of the infection, trap the virus and prevent it from replicating. Finally the battle turns in favor of the body and the viral infection begins to fade. It's been a struggle but you've won and begin the road to recovery.

Vomiting and diarrhea are not common with most types of influenza but have been reported with the 2009 Swine Flu.