What it is: Hepatitis B is a virus that causes liver damage.

How you get it: Transmitted by all bodily fluids, including saliva. You can catch it by kissing an infected person. Any sexual activity: oral, anal, or vaginal. Sharing dirty needles, razors, toothbrushes, nail clippers and unclean implements for body piercing and tattooing.

Symptoms: Rashes, jaundice, fatigue, nausea, vomiting, body aches, abdominal aches, loss of appetite. Some people, however, don't have any symptoms.

Prevention: There's a vaccine for this, given in a series of three shots. Hepatitis B is highly contagious, so you need to avoid intimate contact with people who have it. Barrier methods can reduce risk during intercourse, but you're still at risk if you kiss the person.

Treatment: The vaccine is effective even after exposure. Also, shots of immune globulin help strengthen the immune system to fight it off.

Long-term Implications: If you take very good care of yourself, with rest, a good diet, and no alcohol, and you seek medical help, this disease can run its course. It is, however, chronic and can recur. Untreated and unmanaged, it can lead to liver damage and death.